Choose the correct word for the blank in this sentence: Because of his strength, speed, and skills on the field, Dwayne ____ a perfect candidate for the NBA draft when he graduated from college.

The verb was is of the same tense as graduated that occurs later in the sentence. It completes the thought logically. The word wasn't isn't a good choice because Dwayne seems to be a great candidate. The words is and isn't are in the wrong tense, and isn't also has the same negative connotation as wasn't.