[单选题]
The grand unified theory (GUT) is a sought-after model that would dre q 0;bx;j/iunify three ;43yv.)c)cdqmyr o fyof th) qrym3y;d 4cy. fo)vce four forces of nature. Which force is the one it would not include?
A. gravitational
B. strong
C. weak
D. electromagnetic
