he looked at a photo变问句
问题描述：
he looked at a photo
变问句
答
Did he look at a photo?
What did he look at?
Who looked at a photo?
答
did he look at a photo?
变问句时，由于原句是过去式而非进行时，所以要用did, 然后原句不变，把looked变成现在式，成look.
如果原句是过去式进行时，例: he was looking at a photo. 那变成问句就要用was, 也就是说：was he looking at a photo?
答
what did he look at?
答
What did he look at?