将下列各题所给的句子合并成一个句子，句子意思不变。

将下列各题所给的句子合并成一个句子，句子意思不变。
1.The writer is in the room.He is writing a letter.
2.—Who is flying a kite?—Yang Ming is.
3.Look at the dog,Tom! It's sitting over there.
4.The boys are in the boat.They're singing now.
5.—Where are you going,Sam?—I‘m going to the park.