【问】 (1) Since he has been in the army，he has been in much better health.

(2) Since he joined the army，he has been in much better health.

(3) Since he was in the army，he has been in much better health.

问题1：这三个句子的意义有什么区别?

问题2：句(3) since从句是否指“自他离开军队以后”?

【答】 这三个句子的基本意义是相同的。但暗含的意义却是不相同的。句(1)中的since从句暗含着“他现在仍在军队里”，句(2)中since从句无此含义(可能现在他仍在军队里，也可能现在不在军队里)，句(3)则明确地表明他已不在军队里。

现在来回答第二个问题。since he was in the army并不是指它所表达的时间段(在军队里)的结束点，而是指它所表达的时间段的起点(参军)。这个从句仍应译为：“自他参军以来”。之所以作这种理解完全是根据句意来确定的。请对比：Since I was a child I have lived inEngland.(Shaw)(从孩童时起，我就住在英国。)但是，有时候，since从句则是表达was(were)所表达的时间段的结束点。请对比：

1. It's been ten years since they were last here.

自从他们上次离开这里已经过了10年了。

2. I haven't seen him since we were at school together.

1059 since they lived in New York

自从我们离开学校不在一起以来，我一直没有看到过他。

3. It has been about forty years since a person could turn in paper money and get gold for it.

大约已有40年人们不再能在银行里用纸币换黄金了。

(参见since you were sure)