3. He was in the kitchen at that time. He was helping his mother.(合并为一句) 

He in the kitchen his mother at that time.

2. He was drinking coffee when his sister bought some food.(改为同义句)

 he was drinking coffee,his sister some food.

1. The girl was waiting for a bus when it began to rain.(对画线部分提问) 

 the girl when it began to rain?

5. 直到风逐渐减弱她才出去。

She didn't go out until the wind was .

4. 我昨天晚上直到11点才睡着。

I didn't  until 11 last night.

3. 昨天晚上七点他在看电视。

He  TV at seven yesterday evening/last night.

2. 他在等公共汽车时遭到了袭击。

He was attacked while he  for a bus.

5. —What you ( do) when he arrived?

—I (write) a letter at that time.

4. (2015 •江苏常州)

一Why didnH you watch Running Man on TV?

—I (make) up the music for the coming School Art Festival.

3. After the storm,he found many (fall) trees on the road.