Question

Mustufa ran the 100-meter and 200-meter races but the one he had trained for the hardest was the 400-meter competition.

Which is the best revision of this sentence?
Mustufa ran the 100-meter and 200-meter races (but the one he had trained for the hardest) was the 400-meter competition.
Mustufa ran the 100-meter and 200-meter races but the one he had trained for the hardest (was the 400-meter) competition.
Mustufa ran the 100-meter and 200-meter races but (the one he had trained for the hardest was the 400-meter competition).
Mustufa ran the 100-meter and 200-meter races (but the one he had trained for the hardest was the 400-meter competition).

Answer 1

Mustafa ran the 100-meter and 200-meter races (but the one he had trained for the hardest was the 400-meter competition)

Reason: Because the sentence in parenthesis is complete and all the other answers are at half or incomplete. (Like marking an assignment complete while one page is incomplete.)