Read the sentence below, identifying any pronouns.

Levi, Flaco, and Haman rode their skateboards to the park, but when he sprained his ankle, he had to go home.

What is the BEST way to fix the ambiguous pronoun reference in this sentence?
a. by changing his to their
b. by changing the boys' names to they
c. by changing their to mine
d. by changing the first he to Levi