Question #N1133

A large study recently revealed that those individuals who frequently engage in physical activity report a higher quality of life than those who do not. The study’s findings have led researchers to believe that physical activity may have a positive effect on quality of life.

Which choice best combines the sentences at the underlined portion so that it conforms to the conventions of Standard English?
A. The study’s findings have led researchers to believe that physical activity may have a positive effect on quality of life.
B. The study’s findings have led researchers to believe: physical activity may have a positive effect on quality of life.
C. The study’s findings have led researchers to believe that physical activity may have a positive effect; on quality of life.
D. The study’s findings have led researchers to believe that physical activity may have a positive effect, on quality of life.