Answer:
B. Technician B only
Step-by-step explanation:
An oscilloscope can be used to check the output signal of an optical sensor. The oscilloscope has the functioning of viewing the results in the form of waveform and its time scale settings can be altered to meet the requirements of the results.
A voltmeter cannot be directly used to monitor the output signal of an optical sensor. But a digital multi-meter can be used to check an optical sensor if the digital multi-meter is set on AC - Volt reading mode.