Examples： “In six months，I m going to leave China and go home to work as an engineer。” “Mary hopes to be rich and married with kids in twenty years。” （on the phone）“I` m going to leave my apartment in ten minutes。It takes twenty minutes to get to your apartment by bike，so I` ll probably get to your apartment in half an hour。” “The sun will blow up and engulf the earth in about 100 million years。” 再看“before”： Now let` s look at “before”： 我两周前买了这本书。 Incorrect English： “I bought this book two weeks before。” Correct English： “I bought this book two weeks ago。” 解释： 要表达“从现在开始的某段时间以前”，我们必须用“某段时间+ago”形式，不能把“以前”译成“before”，我们不能用“某段时间+before”形式. 表达“现在开始的两周前”应说“two weeks ago”. 在下面的例子，这种说法适用于任何长度的时间。 Explanation： To express “（a certain amount of time）before now”we have to say “（a certain amount of time） ago.”We cannot just translate “以前”as “before. ”We cannot say “（a certain amount of time）before.”To express “two weeks before now”we say “two weeks ago. ”Notice in the following examples that this way of speaking can be used for very short，very long，and moderate lengths of time. Examples： “Julie just left thirty seconds ago。She is probably walking down the stairs.” “I cooked this rice three hours ago。It` s too cold to eat now.” “Ten years ago Ian graduated from Harvard University with a biology degree”. “The dinosaurs lived 65 million years ago.”