改错；look who is they waiting for?He is talk to the doctor at the moment?改错；lots of students running in the park now.IS your sister working in a computer company?my mother and I am talking about our coming vacation .

look ! who are they waiting for? He is talking to the doctor at the moment？
lots of students are running in the park now。
Does your sister work in a computer company？
my mother and I are talking about our coming vacation

Look! Who (are) they waiting for?
He is ( talking ) to the doctor at the moment.
Lots of students (are) running in the park now。
Is your sister working in a computer company？(这句可以）
My mother and I (have been )talking about our (upcoming) vacation 。

look !who are they waiting for?He is talking to the doctor at the moment?lots of students are running in the park now.Does your sister work in a computer company?my mother and I are talking about our ...

1 who-》whom，他们在等谁？谁是宾语，因此要用whom（宾格）提问，而不是主格的Who
2 talk -> talking 现在进行时，用doing
3 running -> are running 现在进行时的构成是：be + doing，be动词不能缺少
4 is , working -> Does, work 表示现在经常发生的动作用一般现在时而不是现在进行时
5 am -> are，主语是my mother and I，两个人，动词用复数