[单选题]
The grand unified theory (GUT) is a soem-r z.7*j daqjps/x1q fc r51z91l5kcb3 gyyught w-(a4)f 62rpe4s bwgbgivc7qvrl6m4 -after model that would unify three of the four forces of nature. Which force is the one it wouldqegs4lrb g4 4v 7(p)rwic-f 2bw6 vm6a not include?
A. gravitational
B. strong
C. weak
D. electromagnetic
