题目：
按要求改写下面句子。
1. Help was often given to him by us. (改为主动语态)
We often him .
2. Maths is more difficult than any other subject. (改为同义句)
Maths is the difficult all the subjects.
3. I have written to him for a long time. (改为同义句)
He ______ ______ ______ me for a long time.
4. I started to study English two years ago. (改为同义句)
I English for two years.
5. We have an English test once a month. (对划线部分提问)
do you have an English test?
答案：
1. gave…help 2. most…of 3. has heard from
4. have studied 5. How often
