how are lucy and tony.这句话为什么要用are而不用 is?

how are lucy and tony.这句话为什么要用are而不用 is? how old are you 为什么要用are而不用is 为什么Lucy with her friends is(be)from Jpan用is而不用are? jenny and i are quiet 为什么用 are 不用 is how is your study going为什么用is不用are? The writer and teacher is coing now为什么用 is 而不用are? Where are my pens?请问这句为什么不用IS而用are? 为什么用who is it 而不用who are you? Is your mother and you fine?为什么不用are?为什么要用is? lucy and lily is twins 还是Lucy and lily are twins请问哪句话对? How nuch is/are it/they 为什么不用how many? 请问 some of them are students 这句话当中为什么用them而不用they?