At normal temperature, for an echo to be heard the reflecting surface should be at a minimum distance of ………………. m.
A. 34.4
B. 17.2
C. 10
D. 20
Answer:B
At normal temperature, for an echo to be heard the reflecting surface should be at a minimum distance of ………………. m.
A. 34.4 B. 17.2 C. 10 D. 20