单项选择题

设f(x,y)=xey,则=(    ).
   A.0    B.2    C.-1    D.1

A.174.24.96:6088/Latex/latex.action?latex=XGZyYWN7XHBhcnRpYWwgZn17XHBhcnRpYWwgeH1cbWlkIF97XGJlZ2lue2FycmF5fXtjfXg9Mlxc%0D%0AeT0wXGVuZHthcnJheX19'
B.

C.0
D.2
E.-1