past perfect vs. simple past

[Tensy]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #115 "Tense Agreement", question 2

By the time I had reached the bottom of the mountain, I ......... extremely tired.

(a) feel
(b) have felt
(c) felt
(d) am feeling

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #115 "Tense Agreement", answer 2

By the time I had reached the bottom of the mountain, I felt extremely tired.

Correct answer: (c) felt

Your answer was: incorrect
By the time I had reached the bottom of the mountain, I have felt extremely tired.
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when is the best time to use have / had

Tensy

[Mister Micawber]

.
Simply speaking, use present perfect (have done) when the action or the effect of the action continues from the past up to the present time. Use past perfect (had done) when the action or the effect of the action continued from the farther past to the past moment of the other verb.
.
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Native English teacher at Mister Micawber's

[Yankee]

It would be typical to use the simple past tense after 'by the time'. The use of the past perfect (had reached) strikes me a quite odd here.

By the time I reached the bottom of the mountain, I felt extremely tired.

If you wanted to indicate that a feeling of tiredness came only after you reached the bottom of the mountain, then it would be better to use the word 'after' rather than 'by the time'.

After I had reached the bottom of the mountain, I felt extremely tired.
.
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"Nearly all men can stand adversity, but if you want to test a man's character, give him power." ~ Abraham Lincoln

[Johnny04]

Or "By the time I reached the bottom of the mountain, I had felt extremely tired."

[Beeesneees]

That sounds even more odd!
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"Inside every old person is a young person wondering what happened."
Terry Pratchett