化学用语是学习化学的主要工具，按要求用化学用语填空：

2个氮原子　 　．

解：2个氮原子就是在氮元素符号的前面加上数字2，

故答案为：2N．

Some middle school students don't know how 　 　 (keep) a balance between study and play.

答案：to keep

The girl students are sidcussing 　 　 the walls in the classroom.

A. what to paint color B. to paint what color

C. which color to paint D. to paint which color

It takes us less time to go to Beijing because the 　 　 of trains has increased a lot.

A. price B. speed C. space D. service

My parents have a lot of housework 　 　.

A. do B. to do C. doing

Sleeping is a popular way 　 　 among students.

A. relax B. relaxed C. relaxing D. to relax

Can you tell me how to 　 　 the word? I need to get my pronunciation right.

A. pronounce B. pronunciation C. copy D. write

He wants to marry off his daughter to the son of his business 　 　.

A. partner B. worker C. doctor D. patient

The  price of good, drinks and clothes 　 　 so quickly these years.

A. develops B. raises C. improve D. increases

He has a special 　 　 (能力) to write with two hands at the same time.

答案：ability