To hear a distinct echo the time interval between the original sound and the reflected sound must be at least

To hear a distinct echo the time interval between the original sound a

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