Final answer:
The sentence in question is in the passive voice, as the subject 'surgical instruments' is acted upon by being sterilized.
Step-by-step explanation:
The sentence 'To reduce infections, surgical instruments must be sterilized before use.' is in the passive voice. In this sentence, the subject, which would be the surgical instruments, receives the action of being sterilized, rather than directly performing the action. The person or entity responsible for doing the sterilizing is not mentioned, which is a common reason to use the passive form. In contrast, an active voice version of this sentence might read, 'Someone must sterilize surgical instruments before use to reduce infections,' where the subject (someone) performs the action (sterilizes).