第1个回答 2012-01-12
加动词ing形式
be busy doing sth. 忙于做某事
第2个回答 2012-01-12
be busy with sth/n
eg. He is busy with his homework.
be busy doing sth
eg. He is busy doing his homework.
第3个回答 2012-01-12
be busy doing sth. 忙于做某事
第4个回答 2012-01-12
be busy with sth
be busy doing sth