be busy doing是不是省略了介词in

　　A be busy doing sth.

　　意为“忙于做某事”。故选A。

　　Means to be busy doing something.

　　就是指忙着做各种事情。

　　Georgina spends a lot of time pottering about the house pretending to be busy but doing nothing in particular.

　　乔治娜在房子里久久地跑来跑去，装出很忙的样子，但却没做什么事。

　　Since then, however, my husband started to be busy in doing his work so that he had hardly had enough time to talk with my son.

　　然而之后，先生开始忙于工作，几乎没有时间好儿子聊聊。

　　We were locked in.

　　我们被锁在里面了。