Question

read the sentence.

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).

Explanation:

Analyze the original sentence structure

The original sentence is: "Mustufa ran the 100-meter and 200-meter races but the one he had trained for the hardest was the 400-meter competition."
We need to identify the nonessential or parenthetical information that can be set off with parentheses without changing the core meaning of the sentence.

Evaluate parenthetical elements

Using the Parenthetical Elements knowledge point:
A parenthetical element is explanatory or qualifying information that is not essential to the main grammatical structure of the sentence. If you remove it, the remaining sentence must still be grammatically complete and make sense.

• Let's test removing the phrase "the one he had trained for the hardest":

"Mustufa ran the 100-meter and 200-meter races but was the 400-meter competition." (This is grammatically incorrect and does not make sense).

• Let's test removing "but the one he had trained for the hardest was the 400-meter competition":

"Mustufa ran the 100-meter and 200-meter races." (This is a complete, grammatically correct sentence).
Therefore, the entire contrasting clause starting with "but" acts as parenthetical, nonessential information added to the main statement.

Apply parentheses rules

Using the Parentheses Usage knowledge point:
Parentheses must enclose the entire nonessential element.

• Option 1: "...races (but the one he had trained for the hardest) was..." leaves "was the 400-meter competition" disconnected.
• Option 2: "...hardest (was the 400-meter) competition." awkwardly splits the predicate.
• Option 3: "...races but (the one he had trained for the hardest was the 400-meter competition)." leaves the coordinating conjunction "but" outside, which is incorrect because the entire contrastive clause is the parenthetical element.
• Option 4: "...races (but the one he had trained for the hardest was the 400-meter competition)." correctly encloses the entire nonessential clause starting with "but" inside the parentheses.

Answer:

• (A) Mustufa ran the 100-meter and 200-meter races (but the one he had trained for the hardest) was the 400-meter competition.
• (B) Mustufa ran the 100-meter and 200-meter races but the one he had trained for the hardest (was the 400-meter) competition.
• (C) Mustufa ran the 100-meter and 200-meter races but (the one he had trained for the hardest was the 400-meter competition).
• (D) Mustufa ran the 100-meter and 200-meter races (but the one he had trained for the hardest was the 400-meter competition). (Correct answer)