My mother’s age is double of my sister. My father is 20 years elder than me. When my sister was born I was 5 years old. If my sister is at present 17 years old, then what is the difference of ages of my father and mother?
(A) 5 years
(B) 6 years
(C) 7 years
(D) 8 years
Correct option is (D) 8 years