A young man finds that every time he eats dairy products he feels very uncomfoable. His stomach becomes distended. He develops gas and diarrhea frequently. These symptoms do not appears when he eats foods other than dairy products. Which of the following is the most likely enzyme in which this young man is deficient?

The clinical picture is suggestive of lactose intolerance. But lactase is not given in the options. Hence we have to look for an enzyme whose deficiency produces a similar clinical picture. Sucrase-isolamtase deficiency also presents with diarrhoea and bloating (gas) following intake of a diet containing sucrose or glucose polymers.