1) He is busy with his writing.

他忙於写作。
2) He was busily engaged writing letters.

他正忙於写信。
3) He was busy with his writing.

他忙于写作。
4) He is good at English composition.

他善於英文写作。
5) He was busy canvassing for the election.

他忙於竞选活动。
参考词条