Answer:
The mushroom in the picture and the option choices are included in the attached image. below...
The highlighted region of the mushroom in the picture represents the mushroom's "Gills", and paticularlly the multicellular structure carrying the Hymenium called "the basidiocarp" aka basidioma; the Hymenium or underside of the mushrooms is comprised of vertical plates arranged radially, and if a cross section of this is exposed by making a straight cut through the basidiocarp on a microscope, it would appear as option: (A. )