请问大虾们,在这句子为什么是用 were 而不是are呢

请问大虾们,这句子为什么要加have呢 为什么是用were而不是was? 为什么用it is 而不是there are?这个句子的成分如何分析呢? If i were you,i might fly to London.为什么用were呢?而不是was? from the moment they are born为什么用are而不是were? These shoes are made in Italy.为什么这个句子要用are呢?不是用were吗? 为什么是you were very good at basketball 而不是you are very good at 为什么是we were having breakfast, 而不是we are eatting breakfast. 请问各路大虾,sick在这句子里是什么词性 You may feel relaxed after a rest.问下各位大虾,请问此处为什么用relaxed而不是r 表示正在进行的动作要加ING,可能为什么有时句子时会看到是VING而不是ING呢?二者都是在什么情况下用的,本人感激不尽 THE TEACHER SAID THAT THEY WERE GOOD STUDENT,为什么WERE不是ARE呢,这