单项选择题

,则du=(    ).
   A.2xdx-2x2dy
   B.
   C.
   D.

A.174.24.96:6088/Latex/latex.action?latex=dT1cbGVmdCggXGZyYWN7eH17eX0gXHJpZ2h0KV4y'
B.

C.2xdx-2x2dy

D.E.174.24.96:6088/Latex/latex.action?latex=XGZyYWN7Mnh5ZHgtMnheMmR5fXt5XjN9'
F.G.174.24.96:6088/Latex/latex.action?latex=XGZyYWN7Mnh9e3leMn0tXGZyYWN7MnheMn17eV4zfQ%3D%3D'
H.I.174.24.96:6088/Latex/latex.action?latex=XGZyYWN7MnhkeC0yeF4yZHl9e3leMn0%3D'