[单选题]
A block of mass M slides down a fwndgzf-e+n6(q) p 8ubp ie +z5rictionle :)iy +et+:9h istf zjd62wkpwss plane inclined at an angle q with the horizontal. The normal reaction2wsh +d) :i :jtep6zykf9iw t+ force exerted by the plane on the block is
A. $Mg$
B. $Mg \; \sin(q)$
C. $Mg \; \cos(q)$
D. zero, since the plane is frictionless.