Please explain clearly and thoroughly. Answer is C.

20) What compound exhibits three singlets in its proton spin decoupled 13 C NMR spectrum? A) CH3CH2CH2CH3 B) (CH3)2CHCH(CH3)2 C) BrCH2CH2CH2Cl D) (CH3)2CHOCH(CH3)2 E) BrCH2CH2CH2Br