6. The positive integer solutions of the equation $\frac{4}{m}+\frac{2}{n}=1$ are ( ) groups.
(A) 2
(B) 4
(C) 6
(D) 8
6. B.

The equation is transformed into $(m-4)(n-2)=8$. Solving, we get
$$
(m, n)=(5,10),(6,6),(8,4),(12,3) \text {, }
$$

There are four sets of positive integer solutions.