A simile is a right figure of speech that should be used in this sentence. Hence, the correct answer is option A. Simile.
Basically, Simile is a figure of speech that involves the comparison of one thing with another thing of a different kind. Heretwo, unlike things, are compared explicitly. Most of the times, Simile uses two words “as” and “like” for describing any comparison. The above-given sentence has used “as” word to describe a comparison between a lion and a boy. That’s why it resembles “Simile”.