Which word is the subject complement of the sentence?

Neil Armstrong was the first human to walk on the moon.

A. walk

B. Armstrong

C. moon

D. human

The correct answer is D) the subject complement of this sentence is human. A subject complement is a word (usually a noun) which follows a linking verb (which connects two parts of a sentence - in this sentence, the linking verb is was), and refers to the subject of the sentence. Here, the word human refers to the subject Neil Armstrong, he is that human.