Answer:
B. The best class in the school finished the test in less than 10 minutes.
Step-by-step explanation:
You can identify an active voice in a sentence if it contains a subject that reflects the intention of the verb. An active voice will usually begin with a subject in a sentence. In a sentence, an active voice contains a subject, verb, and object.
To further enhance your understanding, I will be citing a few examples. These examples are; I passed my English exams, Mary Jane wrote the poem, the vehicle hit the train, etc.
Option B is the answer because the subject "Class" does the action described by the verb "finished".