—What do I have to do I want to be thinner?—Eat less exercise more.A. butB. sinceC. beca

问题补充：

—What do I have to do I want to be thinner?—Eat less, exercise more.

A. but

B. since

C. because

D. if

答案：

A. but

B. since

C. because

(答案→)D. if

解析：本题考查连词。根据前后文的联系，可知是假设关系，即要用条件状语从句，故选D。句意：——如果我需要变得更瘦点，我不得不怎么做？——少吃，多锻炼。