为什么不是since i started to play football 而是got to play?不是也有start to

为什么不是since i started to play football 而是got to play?不是也有start to it is two years since I started learning English这个句子对吗?为什么? It's______ a long time since I started to teach at this school为什么 it is over a year since i met him 为什么要用since since前不是要用完成时吗? Several years has passed since we started our middle school life.这里为什么是has passed?several years不是复数形式吗,为什么不是用have passed Two months has passed since i started to study at Beijing University为什么是用has 不是 have 老师讲的我没听懂、、、 明天期中考 they hadn't sailed for long.they hadn't sailed for long____ a violent storm started,A after B.since C.when D.while为什么不是B呢. I have had thousands of classes since I started school nine years ago. I started collecting coins when I was thirty.(用since改写） I started collecting coins when I was thirty.(用since改写) 翻译I've wanted an exercise bike since I had children and started putting on weight. before i started high schol i used to spend a lot of time playing games whit my friend 为什么为什么不是过去完成时，不是在过去的过去 It had been many years since my wife and I had gone dancing it + 过去完成时 + since + 例句：it + 过去完成时 + since + 过去完成时为什么不是it + 过去完成时 + since + 过去式?真的是it + 过去完成时 + since + 过去 I have started to study English since two years ago 怎么改 It's quite a lng time since I started to teach at this school.翻译. it has been two days since I started study.这句子对吗? I have been here since I was born 和I haden't seen him since he left NANJING.两句话为什么用的不是相同的时态? i'm starting to lose wight since i started going to the gym.第个start为什么跟to do形式?第2个start为什么又是跟doing 的形式?搞不懂呀