我是来发坏的。。。
自己查这个题目的时候本来自己对when和if的理解基本上同suri的总结,然后在BTG论坛上看到一个哥们儿的解释(还是个instructor),粘贴如下:
Great question! The difference between 'when' and 'if' is a subtle one. Indeed, in many cases the two are interchangeable. Let's have a look:
'If' and 'When' are interchangeable if the outcome is clear.
When John runs 5 miles, he sweats.
If John runs 5 miles, he sweats.
John's sweating is definite. No matter what, he will sweat if/when he runs 5 miles. Thus the outcome is clear and we can use either 'when' or 'if.'
'If' and 'When' are NOT interchangeable if the outcome is not clear. That is we are dealing with the Conditional Tense. Then we want 'if.'
It's hot outside, so John may sweat, if he runs one miles. CORRECT
It's hot outside, so John may sweat, when he runs one mile. INCORRECT
In the question above, we have an outcome that is not definite: inventories...can lead.
Therefore, we want 'if' not 'when.' Because we have inventories, (D) is incorrect (...leads).
Hope that helps .
不过我个人对以上解释持怀疑态度,个人还是比较相信原来的总结。。。
-- by 会员 zhongshanlh (2012/4/25 12:26:34)