Assertion (A) : Z > 1 for H₂ and He at all pressures at ordinary temperature.  

Reason (R) : Repulsive forces acting between them overcome the attracting forces at ordinary temperature.

So, the repulsive forces acting between them overcome the attracting forces and as a result, the actual volume of the gas becomes something more than the ideal value. - It is seen that Z is greater than one for hydrogen and helium at all pressure and it increases with increase in pressure.