现在进行时:
肯定句:He's climbing a tree.
疑问句: Is he climbing a tree?
否定句: He isn't climbing a tree.
一般过去时:
肯定句:He climbed a tree.
疑问句: Did he climb a tree?
否定句: He didn't climb a tree.
将来时:
肯定句:He's going to climb a tree.
疑问句: Is he going to climb a tree?
否定句: He isn't going to climb a tree.
现在完成时:
肯定句: He's climbed a tree.
疑问句: Has he climbed a tree?
否定句: He hasn't climbed a tree.本回答被提问者采纳