Explain the effect of the mutation that occurs among northern european on lct gene expression

Lactose tolerance and intolerance together with other northern European individuals Lactose, the sugar found in dairy items and drain, is processed by the catalyst lactase. 
Lactose intolerance is a typical stomach related issue where the body can't process lactose, a sort of sugar mostly found in drain and dairy items. Manifestations of lactose intolerance, as a rule, create a couple of hours of devouring nourishment or drink that contains lactose.

The answer is b. hope this !