I didn`t finish writing my test.和Amy started skating when he was nine.的动词finish、start后为什么要跟动词的ing形式?谢谢······

You didn't finish the project.I didn't finish the project,either用neither...nor合并句子 I___my homework,I guess I can‘t join you.A.don't finish B.didn't finish C.haven't finished ↓D.won't finish I didn't finish the work on time.Alice didn't didn't finish it,either(合并为一句） I didn't go home until I finished my homework 中 finish 为什么加ed? I didn't finish ________(write) my test because I ran out of time. I'm sorry I didn't finish ______（write） my composition ---Didn't you finish your school work?---______A.no i didn't B.yes i didn'tC.no i did 说明理由, I didn't finish my homework on time.It made my teacher___(happy) 关于write短语请给我一个词组在用这个词组造句．词组中含有write例如：To writ back 造句：I dent him letter but he didn't write bank You didn't finish your homework yesterday,did you?( ).I had no time to do it becausu of illnessA.Yes,I didn't.B.No,I did.C.Yes,I did.D.No,I didn't. I didn't finish my test because I _______ time. A.run out of B.ran out of I didn't finish it.-------___________________A.So was iB.So did iCneither was iD.neither did i he didn't know how he could break the ropes同义句he didn't know____ _____ _____the ropesi will stay at home until i finish my homework(同义句）i ____ _____ _____until i finish my homework i didn't want I didn’t know i didn't see I didn't play I （）my homework,I guess I can't join you.A.don't finish B.didn't finishC.haven't finishedD.won't finish答案是选C,可我选的A,为什么?