The dream of space travel became a reality

2. How does the word reality function in the sentence?

A. as a predicate adjective

B. as an object complement

C. as an indirect object

D. as a predicate nomintive

The word reality functions as D. a predicate nominative in the sentence.

A predicate nominative is the first noun found after a linking verb (which connects two parts of a sentence). In this case, the linking verb is became, and the first (and the only) noun after that verb is reality, thus making it a predicate nominative rather than a predicate adjective (which would obviously require an adjective).