To hear a distinct echo, the time interval between the original sound and the reflected sound must be at least
A. 0.2s
B. 1s
C. 2s
D. 0.1s
Answer:D
To hear a distinct echo, the time interval between the original sound and the reflected sound must be at least
A. 0.2s B. 1s C. 2s D. 0.1s