[单选题]
The grand unified theory (GUT) idnks27lwq/ m960w dk xs a sought-after model that would unify threxpejw; m1;j -0x lgmm:e of the four forces of nature. Which fe -jwgxp0 lmxm:1; ;jmorce is the one it would not include?
A. gravitational
B. strong
C. weak
D. electromagnetic
