When a gas in a cylinder is compressed at constant temperature by a piston, the pressure of the gas increases. Consider the following three statements.

a) The rate at which the molecules collide with the piston increases

b) The average speed of the molecules increases

c) The molecules collide with each other more often

Which statement(s) correctly explain the increase in pressure?

• A

  a only

• B

  b only

• C

  a and b only

• D

  a and c only