The degree of the internal angle of a regular triangle is 180-360 ÷ 3 = 60, and the degree of the internal angle of a regular quadrilateral is 180-360 ÷ 4 = 90, 3× 60+2× 90 = 360, so three regular triangles and two squares can be used for plane splicing.

The degree of an internal angle of a regular hexagon is 180-360 ÷ 6 = 120, 2× 60+2× 120 = 360 or 4× 60+ 120 = 360, which can be used for plane.

Any number of regular quadrangles and regular hexagons can't form a plane mosaic. There are two different combination selection methods.

So choose B.