6.

Answer and Explanation

Your Answer is

Correct Answer is H

Explanation

According to the meaning of the sentence, Blades thinks that this reform will become possible...so the attributive clause should be used here to modify reform, excluding F/G.

Item J: Although it is an attributive clause, believing (not a predicate verb) cannot be used as a predicate of Blades, so it is wrong.

Item H: which modifies reform, the subject in the object clause guided by believe in the clause, that is, Blades believed (the reform) would be possible only if...