Final answer:
The sentence "The Tigers lost the playoffs." is in active voice because the subject 'The Tigers' is performing the action of losing without the use of a 'to be' verb and a past participle.
Step-by-step explanation:
The sentence "The Tigers lost the playoffs." is in active voice. In this sentence, 'The Tigers' is the subject and 'lost' is the verb. The subject is performing the action, which is losing the playoffs. The sentence does not contain a form of the verb 'to be' followed by a past participle, nor can the preposition 'by' be added to make logical sense, which are the hallmarks of passive voice.
To further illustrate, we can compare this sentence to one written in passive voice: 'The playoffs were lost by the Tigers.' See how the subject of the sentence, 'The playoffs,' is receiving the action and 'by the Tigers' indicates who performed the action. This restructured sentence demonstrates classic passive voice construction, in contrast to the original active voice sentence.