This is my 2nd posting on the tense issue.
Please look at the following question.
After he (won) the marathon relatively (easily), he decided to continue his training program and (even to ener) more races. (No error)
correct answer is (won) which should be (had won).
But I think we could use either (won) or (had won), therefore, the answer should be (no error). What do you think? Why do we have to use (past perfect) when it is obvious that winning the marathon happened first because of “after”?
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Hello, I’m ‘The French’, I prefer the use of the past perfect.
The Past Perfect it uses for one action that happens before another in the past.
In your example, when he won the matathon after he decided to continue her training, to entend win another races (but I’m not a teacher).
Bye. 
thank you for your reply.
But doesn’t the conjunction “after” clearly shows which action took place first?
I looked up some grammar books, and many of them say that when you use conjunctions like after or before, replacing “past perfect” with “simple past” is acceptable.
that’s why I’m confused here.
anyone else to comment on this issue?
thanks