In a certain alphabet, 16 letters contain a dot and a straight line. 30 letters contain a straight line but do not contain a dot. If that alphabet has 50 letters, all of which contain either a dot or a straight line or both, how many letters contain a dot but do not contain a straight line? Choose the most appropriate option.
A) 4  B) 8  C) 12  D) 16  E) 20

Rationale: "we are told that all of the letters contain either a dot or a straight line or both , which implies that there are no letters without a dot and a line ( no line / no dot box = 0 ) . first we find the total # of letters with lines : 16 + 30 = 46 ; next , we find the total # of letters without line : 50 - 46 = 4 ; finally , we find the # of letters that contain a dot but do not contain a straight line : 4 - 0 = 4 . answer : a"
Answer: A