[单选题]
The grand unified theoreu(oba,b*c:q 7 yujj 1y (GUT) i3sfm-uw1zgilt-mz : ) s a sought-after model that would unify three of the four forces of nature. Which force is thefl--ug13mzisz ) t mw: one it would not include?
A. gravitational
B. strong
C. weak
D. electromagnetic
