CRO measures time-based wave properties directly

Steps:

• CRO displays sound wave as voltage versus time trace.
• Time axis on CRO gives horizontal distance between wave peaks.
• This distance equals one period of the wave.
• Period is calculated as time per cycle from the trace scale.

Why B is correct:

• Period is the time for one complete wave cycle, directly measured from the time-base setting and peak-to-peak distance on CRO.

Why the others are wrong:

• A: Amplitude requires voltage scale info, but sound waves need pressure or intensity, not just CRO voltage.
• C: Speed needs distance traveled, unavailable on CRO's time-only display.
• D: Wavelength requires physical distance in medium, not provided by CRO.

Final answer: B