纠正几个句子：
He is painting the door.
s v o
He is watching the flowers.
s v o
They were building that bridge {when I was there}.
s v o
The students asked him （a lot of） questions.
s v 间接o 直接o
{Where} do they sell （this kind of） TV set?do和sell都是v,被s分开了.
v S v o
When} did they hold the meeting?同上
v S v o
Who does he {often} help?
O v s v
其他的疑问句都是这样,你可以自己改一下.