若函数 f(x)为可微函数，则dy（ ）

A、[imgsrc="http://cdn.mathpix.com/snip/images/4c6gQGa_5UXllr_0lbWWN2EorbvEhpNz3ypprJEJyU
A、original.fullsize.png"]
B、[imgsrc="http://cdn.mathpix.com/snip/images/JhZp5zksvS_TomjffbrhB2eZf9gu12DKMbc88Y8JxXo.original.fullsize.png"]
C、[imgsrc="http://cdn.mathpix.com/snip/images/4VsD24uSHpYntrBktSU1afE7lrIjufM1TVJNc9Fg3v
E、original.fullsize.png"]
D、[imgsrc="http://cdn.mathpix.com/snip/images/k8IlHyivJ2VwST6RYBE1dO3Eab05eeycxpVYnLS4hXM.original.fullsize.png"]