Two babies with kidney stones receive medical treatment at a military hospital in Lanzhou, Sept, 11, 2008. [Xinhua]

       A first round research has confirmed the Sanlu baby milk powder polluted by melamine(三聚氰胺) was the cause of kidney stones in babies, said an official statement.

       The melamine found in some of the Sanlu products was deliberately added to increase the protein (蛋白质) percentage in raw milk or milk powder, it said.

79．Please fill in the blank with proper words or phrases．（Please answer within 10 words．）

78．Please translate the underlined sentence in the passage into Chinese．

77．Find out the sentence in the passage which can replace the following one．

  It shouldn’t be generally considered that it was the disturbance to others that led to the popularity of silent reading.

76．What is the writer of this passage attempting to do? （Please answer within 10 words．）

       73.    But then, instead of swallowing their dinner immediately, the snakes sit back and wait for their preys to become safe to eat. That's because both the Dahl's frog's protective toxin(毒素) and the marbled frog's glue break down over time. After a while, the frog toxin is no longer poisonous and the glue is no longer sticky.

       74．   and floodplain death adders seem to know the difference, And adder waits for a different length of time depending on the species of frog it just struck.

       The stickiness of the marbled frog glue decreased by as much as two-thirds after just 10 minutes. And that's just about how long an adder waits before eating a marbled frog.

71.   But to a type of Australian snake, this rude behavior is a matter of life and death.

       The snake, called a floodplain death adder(蝰蛇), eats two types of frogs that are hard to stomach. The frogs produce chemicals to defend them from predators（猎食者）.

     72 .     The other species, the marbled frog, is less dangerous but still tough to eat. When attacked, it produces a glue like substance. Leaves and branches get caught up in this material, making a big sticky mess that gets in the way of anything trying to swallow it. A marbled frog can even get stuck on the head of an attacking snake.

       Both frogs have good defense methods. But the floodplain death adder knows how to get around each of them.

70. It can be inferred from the last two paragraph that_____.

A. the rate of teen smoking is far lower than it was

B. cigarette smoking can be stopped sooner or later

C. there is a different idea about the drop in teenage smoking

D. no younger teens really understand the dangers of smoking

第二节根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。（答案写在答题纸上）