When he returned he was accompanied by a sprightly young girl.

The correct answer is C. lively.

A sprightly young girl is one who is full of life and energy. She is cheerful and animated, and she enjoys being active. She is also often playful and fun-loving.

Sportive means fond of or good at sports. Intelligent means having or showing

While a sprightly young girl may be any of these things, the word “sprightly” specifically emphasizes her liveliness and energy.