Jack hurt his back playing volleyball.为什么用palying?什么语法?

Jack hurt his back playing volleyball.为什么用palying?什么语法? 为什么Jack hurt his back playing volleyball中的play用的是ing形式而不是过去式? His back（ ）A、hurt B、hurts C、is hurt going Jack is going back to his school. Jack _____(leave) until his teacher comes back. Jack _____(leave) until his teacher comes back.why? 同义句转换:Jack left China after his wife came back.Jack left China after his wife came back.Jack ( ) ( )China （ ） his wife came Jack hurt his arms in a car accident yesterday.改为一般疑问句 Jack fell ____ and hurt his leg.off down behind选择哪个? Jack ______ (hurt) his ankle last month and he ______ (have) to walk with crutches now. Jack ran to school .His schoolbag was on his back 同义句转换 Jack ran to schooll ,his schoolbag was on his back改为同义句 A fire fighter _____by burning wood that fell on his back.A was hurt.B.hurt .为什么选A.hurt不是可以用主动表示被动么. “He hurt his back playing basketball”中“playing basketball"的成分. Jack hurt his hand ( )play volleyball.用to play还playing答案是playing,为什么不能用to play jack and his mother (did ) not go to back to their home (until) it gets dark jack and his mother ( ) not go to back to their home () it gets dark 英语改错 My boss is work because he's hurt his back a英语改错My boss is work because he's hurt his back againWe usually have dinner quite early.we're always starving when we get home work