The correct answer is: was sent.
The verb “to send” is used to describe the action of causing someone or something to go somewhere. In this case, the patient is being sent home after a thorough examination. The verb “to send” can be used in the active voice or the passive voice. In the active voice, the subject of the sentence performs the action. In the passive voice, the subject of the sentence receives the action. In this case, the sentence is in the passive voice, so the subject of the sentence (the patient) receives the action (being sent home).
The other options are incorrect because they do not agree with the tense of the sentence. The sentence is in the past tense, so the verb must also be in the past tense. Option A, “was sent,” is the only option that is in the past tense. Options B, “were sent,” and C, “are sent,” are in the present tense. Option D, “to send,” is in the infinitive form.
In conclusion, the correct answer is: was sent.