Which of the following sentences uses the word envious correctly? A. The toy store sold envious and clothing for children.
B. Before going to the envious, make sure you find your tennis racquet.
C. Marcia was envious when Gabby got a new car for her birthday.
D. At the store, the men were acting envious and the manager thought they might steal something

C. Marcia was envious when Gabby got a new car for her birthday.

Explanation:

Envious means "feeling or showing envy" and as that isn't super helpful (jk), envy means having a feeling of discontented or resentful longing aroused by someone else's possessions, qualities, or luck. In the examles, the only one showing this is when Marcia ia envious of Gabby, she wished she has her possession (care), etc.

Fun fact: Jealousy is sometimes used when envious should be :D

(although they are quite similar, to be jealous can also means "fiercely protective or vigilant of one's rights or possessions" and jealousy is the act of being envious, it's kind of confusing