Correct Answer - C
`P (V-b) = RT`
`rArr PV = Pb = RT`
`rArr (PV)/(RT) = (Pb)/(RT) +1`
`rArr Z = 1+(Pb)/(RT)`
Hence `Z gt 1` at all pressure.
This means, repulsive tendencies will be dominant when interatomic distance are small.
This means, interatomic potential is never negative but becomes positive at small interatomic distances.
Hence answer is (C )