Our teachers are very busy. They have not had a day ________ for a week.

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Mr Green is a doctor of ________ and his daughter Ann is ________ college student.

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A．50 years old; an 18-year-old

B．50-year-old; an 18 years old

C．50 years old; a 18-years-old

D．50-years-old; a 18 year old

In class, you should concentrate your attention ________ your lessons.

[　　]

Jim doesn't do his homework ________. So he always makes a lot of mistakes.

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The teachers in our school are all hard-working. They are not only very strict ________ their work, but also strict their students.

[　　]

--- I went to the farm to help pick apples yesterday.

--- ________.

[　　]

This kind of food ________ cool, clean and dry according to the instructions.

[　　]

Liu Yu, a good runner, is serious ________ running.

[　　]

Do you know what will happen if he ________ succeed?

[　　]

Sometimes teenagers' hobbies can get ________ the way school.

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