单项选择题

A.

B.a+b
C.b-a
D.E.174.24.96:6088/Latex/latex.action?latex=XGZyYWN7YStifXsyfQ%3D%3D'
F.G.174.24.96:6088/Latex/latex.action?latex=XGZyYWN7Yi1hfXsyfQ%3D%3D'