[单选题]
The grand unified theory (GUT) is a sought-after mode.7k .ldk*v e.bbmma/o l that would unify three8l5a zc f 647vsifms4b of the four forces of nature. Which force is the one it would not is86ab 4msvzi75lf fc 4nclude?
A. gravitational
B. strong
C. weak
D. electromagnetic
