21. rise/ raise/ arise/ arouse
They their output by more than half in less than three years.
His voice in excitement.
Accidents from carelessness.
We must them to fight with enemies.
22. acquire/ require/ inquire （enquire）
The pilot about the weather condition.
The occasion formal dress.
Gradually we experience in how to do the work.
23. contract/ contact/ contest/ contrast/ context/ content/
Metal as it becomes cool.
Use the following information to get in touch.
He's the election next week.
Today's work is quite a to what you did yesterday.
You can always tell the meaning of a word from its .
The police emptied her bag and examined the .
24. reply/ apply/ supply/ comply
Our literature ought to with the popular taste.
Cows us with milk.
In this way they can better theory to practice.
Don't for that job. You're in danger of overreaching yourself.
Tom that he had finished the work.
25. stimulate/ simulate/ accumulate/ formulate
Snow on the ground.
Pinyin can be used on computers to Chinese words now.
The central government policy and measures for speeding up west development.
Some moths（蛾） dead leaves.
Alcohol the action of the heart.
答案：
21. raised, rose, arise, arouse
22. inquired, requires, acquired
23. contracts, contact, contesting, contrast, context, contents
24. comply, supply, apply, apply, replied
25. accumulated, formulate, formulate, simulate, stimulates
