Respuesta :

eIIa

C. vigorous

"vig·or·ous

/ˈviɡ(ə)rəs/

adjective

strong, healthy, and full of energy.

'a tall, vigorous, and muscular man'

characterized by or involving physical strength, effort, or energy.

'vigorous aerobic exercise'

(of language) forceful.

'a vigorous denial'" - Oxford Languages

Answer:

Superfast

Explanation:

Key word is speed here because energetic and vigorous are basically the same meaning and nowhere in the sentence it says anything about the energy of the horse. Superfast and breakneck also basically mean the same thing however I think this sentence wants you to use the term superfast because breakneck means like a dangerously fast speed and it also doesn't say anywhere in the sentence that the horse is dangerous.