B. a sound wave that he could just barely hear
D is the answer and also I love u
Answer:
Explanation:
Doppler radar works by sending <u>a beam of electromagnetic radiation waves, </u>tuned to a precise frequency, at a moving object. You can use Doppler radar on a stationary object, of course, but it's fairly uninteresting unless the target is moving
Answer:
It has mass, it takes up space
Explanation: