I wish very much you ________ manage to come over.

1. A.
   will
2. B.
   can
3. C.
   could
4. D.
   are able to

Bicycle lights may not exactly be a problem that needs solving, but the following can be said about most of them ---- they’re easily stolen if left on an unattended bike. People riding at dusk can forget to turn them on, and those same people can forget to turn them off when they reach their destination. Well, the makers of the Blink/ Steady Bike Light have set out to address all of those shortcomings.

The waterproof(防水的) Blink/ Steady is so far only available as a tail light, although a head light is on the way. It’s fixed onto the bike’s seat post. A built- in photosensor(感光器) tells when it’s become dark enough for the light to be required, and allows it to come on once you begin the riding. According to the producers, it isn’t fooled by things such as headlights or streetlights. The light also contains an accelerometer, also known as a motion sensor, which can tell when the bike is in motion.

Between the two sensors, this means the light will come on only once it’s dark enough, and the bike is moving. Even when stopped at red lights, the small movements of the rider will reportedly be enough to keep the light activated---- it’ll go out after 30 seconds of complete inactivity. While this does mean that the two sensors are continuously powered up, they go into a very low---- power sleep pattern when the bike is sitting, unused.

Light is provided by two5- watt LEDs, seeable over a range of 180 degrees. And power comes from two AAA batteries, which provided up to 200 hours of continuous run time. The designers and engineers behind the Blink/ Steady are now raising money for its commercial production. About US $95 will get you one if they become available.

1.The first paragraph is mainly to mean that______.

A. bicycle lights are worth a research

B. bicycle lights are not a problem at all

C. bicycle lights are easy to deal with

D. bicycle lights are difficult to turn off

2.According to the text, the Blink/Steady Bike Light is sensitive to______.

A. the weather       B. streetlights      C. headlights      D. natural light

3.Why is there an accelerometer in the Blink/ Steady Bike Light?

A. To protect the bike against water.

B. To tell if the bike is moving.

C. To make the bike easy to ride.

D. To judge the speed of the bike.

4.What can be inferred about the Blink/ Steady Bike Light?

A. It will be turned off immediately if the bike stops.

B. The traffic lights have no effect on the light.

C. It won’t use any power if the bike is unused.

D. It must meet two requirements if it comes on.

Below is a selection from a popular science book.

If blood is red, why are veins (静脉) blue?

Actually, veins are not blue at all. They are more of a clear, yellowish color. Although blood looks red when it’s outside the body, when it’s sitting in a vein near the surface of the skin, it’s more of a dark reddish purple color. At the right depth, these blood-filled veins reflect less red light than the surrounding skin, making them look blue by comparison.

Which works harder, your heart or your brain?

That kind of depends on whether you’re busy thinking or busy exercising. Your heart works up to three times harder during exercise, and shifts enough blood over a lifetime to fill a supertanker. But, in the long run, your brain probably tips it, because even when you’re sitting still your brain is using twice as much energy as your heart, and it takes four to five times as much blood to feed it.

Why do teeth fall out, and why don’t they grow back in grown-ups?

Baby (or “milk”) teeth do not last long; they fall out to make bigger room for bigger, stronger adult teeth later on. Adult teeth fall out when they become damaged, decayed and infected by bacteria. Once this second set of teeth has grown in, you’re done. When they’re gone, they are gone. This is because nature figures you’re set for life, and what controls regrowth of your teeth switches off.

Do old people shrink as they age?

Yes and no. Many people do get shorter as they age. But, when they do, it isn’t because they’re shrinking all over. They simply lose height as their spine (脊柱) becomes shorter and more curved due to disuse and the effect of gravity (重力). Many (but not all) men and women do lose height as they get older. Men lose an average of 3-4 cm in height as they age, while women may lose 5 cm or more. If you live to be 200 years old, would you keep shrinking till you were, like 60 cm tall, like a little boy again? No, because old people don’t really shrink! It is not that they are growing backwards—their legs, arms and backbones getting shorter. When they do get shorter, it’s because the spine has shortened a little. Or, more often, become more bent and curved.

Why does spinning make you dizzy (眩晕的)?

Because your brain gets confused between what you’re seeing and what you’re feeling. The brain senses that you’re spinning using special gravity-and-motion-sensing organs in your inner ear, which work together with your eyes to keep your vision balance stable. But when you suddenly stop spinning the system goes out of control, and your brain thinks you’re moving while you’re not!

Where do feelings and emotions come from?

Mostly from an ancient part of the brain called the limbic system. All mammals （哺乳动物）have this brain area — from mice to dogs, cats, and humans. So all mammals feel basic emotions like fear, pain and pleasure. But since human feelings also involve other, newer bits of the brain, we feel more complex emotions than any other animal on the planet.

If exercise wears you out, how can it be good for you?

Because our bodies adapt to everything we do to them. And as far as your body is concerned, it’s “use it, or lose it”! It’s not that exercise makes you healthy; it’s more that a lack of exercise leaves your body weak and easily affected by disease.

1.What is the color of blood in a vein near the surface of the skin?

A. Blue      B. Light yellow

C. Red        D. Dark reddish purple

2.Why do some old people look a little shrunken as they age?

A. Because their spine is in active use.

B. Because they are more easily affected by gravity.

C. Because they keep growing backwards.

D. Because their spine becomes more bent.

3.Which of the following statements about our brain is true?

A. In the long run, our brain probably works harder than our heart

B. When our brain senses the spinning, we will feel dizzy.

C. The brains of the other mammals are as complex as those of humans.

D. Our feelings and emotions come from the most developed area in our brain.