改错；look who is they waiting for?He is talk to the doctor at

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

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...

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 coming vacation