Sound cannot travel in:

1. gases
2. liquids
3. solids
4. vacuum

The minimum distance required between the source and the reflector so as to hear the echo in air is:

1. 10 m
2. 17 m
3. 34 m
4. 50 m

The speed of sound in water is:

1. 332 m s^-1
2. 1500 m s^-1
3. 5000 m s^-1
4. 1000 m s^-1

Sound travels the fastest in:

1. liquids
2. solids
3. gases
4. vacuum