Correct answer is (a) reversible inhibition
For explanation I would say: Reversible inhibition is one where in loss of activity of activity may be revived by removal of inhibitor. As compared to, irreversible inhibition where the loss of activity cannot be restored. Mixed inhibition is one where in both EI and ESI complexes are formed with no product formation. Competitive inhibition occurs when both substrate and the inhibitor compete for binding to active site.