Correct option is B
Suppose that the per cent of the other 75 questions which he needs to answer correctly to score 60% overall is x. Thus, by the given condition,
= 80% of 75 + x% of 75 = 60% of 150
= 80×75+75x=60×150
75x=9000−6000
x=3000/75
x = 40%