Sound cannot travel in:

1. solid
2. liquid
3. gas
4. vacuum

When sound travels in form of a wave:

1. the particles of medium move from the source to the listener
2. the particles of medium remain stationary
3. the particles of medium start vibrating up and down
4. the particles of medium transfer energy without leaving their mean positions.

The unit of loudness is:

1. cm
2. second
3. hertz
4. decibel

In a piano, pitch is decreased by:

1. using thicker string
2. increasing tension
3. reducing length of string
4. striking it hard