that boy is busy ()reading the book ,her mother is busy()her clothes.

问题描述:

that boy is busy ()reading the book ,her mother is busy()her clothes.

that boy is busy (in)reading the book ,her mother is busy(with)her clothes.
be busy in doing sth 表示过去或现在着重干/忙于某事.
be busy with sth 表示现在忙于某事