将下列表示单数的句子改成复数的句子。

1. This is a box.

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2. Do you have a new radio?

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3. There is one peach in my hand.

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4. She has a camera and an umbrella.

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5. He is a driver.

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6. That is her watch.

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7. He is a policeman.

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8. He has a good friend.

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9. What is that?

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10. This is a tomato.

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两样本均数差别的显著性检验用t检验的条件是（）

A.两总体符合正态分布

B.两总体均数相等

C.两总体方差（标准差的平方）相等

D.两样本例数很大

E.两样本分组一致