<span>Él es un compañero de clase is the right answer. The 1st sentence is ella but </span>compañero should be compañera. In the second one ella should not have an accent mark and in the last one el doesn't match with una.
I think the answer is A. Correct me if I’m wrong please
Good question In Spanish, the word "agua" which means 'water' is a special feminine noun. ... Because feminine singular nouns beginning with a stressed "a-" or "ha-" take the definite article “el” not “la” as you might expect. The reason has to do with pronunciation; "la agua" would sound like "lagua" and it might be confusing.
