示例：
(one year ago)
(now)
He played basketball one year ago.
He plays football now.
1．
(two years ago)
(now)
__________________________________________________ __________________________________________________2．
(many years ago)
(now)
__________________________________________________ __________________________________________________3．
(three months ago)
(now)
__________________________________________________ __________________________________________________ 
(one year ago)
(now)
(two years ago) 
(now)
(many years ago) 
(now)
(three months ago) 
(now)
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