单选．

Walking, jogging and swimming are popular ________ of exercise.

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________ breakfast makes you healthy.

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Cats make me ________ , but they make my partner ________.

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Eating the right food and with the right amount ________ you ________.

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What kind of foods do you usually have ________ lunch?

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Why ________ we have hamburgers?

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You ________ to have breakfast every day.

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What about ________ a new cap?

I don't like the math class, ________, because it's too hard.

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The students are sitting ________ the computers. They are having a computer class.

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