The Differential Equation $( x - 2 y ) d x + y d y = 0$

Multiple Choice

The differential equation $( x - 2 y ) d x + y d y = 0$ can be solved using the substitution

A) $u = x y$
B) $u = y / x$
C) $u = x - 2 y$
D) $u = y$
E) it cannot be solved using a substitution