Answer: The sentence that has been written in the active voice is "Marcus threw the baseball to his teammate".
Explanation: A sentence is written in the active voice usually when the subject is performing the action denoted by the verb. In contrast, when a sentence is written in the passive voice, the subject is being acted upon by the verb. The construction of a sentence in the active voice is generally Subject + Verb + Direct Object. In that way, the first sentence ("Marcus threw the baseball to his teammate") has been written in the active voice: "Marcus" is the subject, "threw" is the verb, "the baseball" is the direct object and "to his teammate" is the indirect object. Moreover, in this case, "Marcus" performed the action of throwing.
