suddenly millie heard someone ( )in the next room 1cry 2crying 3cried 4cries

问题描述:

suddenly millie heard someone ( )in the next room 1cry 2crying 3cried 4cries

2crying为什么?crying是现在分词作宾补,表进行的意义,表示宾语someone当时正在主动发生着该动作。