根据下列各句句意及所给中文写出该单词的正确形式。

1.Christmas is one of the main ________________ (节日)in the United States.

2.Although he is over 70, he is still full of _____________(精力).

3.Be careful! This piece of statue is very _________________（珍贵的）.

4.Although I hadn't seen Mary for years, I _______________(识别出) her voice on the phone at once yesterday.

5.The students are shown how to do many simple _________________（实验）in the lab.

6.He has very ____________(锐利的) eyes; he catches sight of things quickly.

7.The ______________ (主题) of the book is the relationship between people and nature.

8.Knowledge and __________________ (创造力) are equally important for a scientist.

9.It is _______________(极其地)hot outside. I have never experienced such a hot summer in my life.

10.Sixty _______________ (百分比) of the students in our class were against the plan, so he had to give in.