In this grid the third figure of every row and of every column is made from the first two. Which figure completes the grid?

Lay the first two figures of a row on top of each other and keep every line: the top row gives lines to the top, top-right and right, and a line drawn in both figures appears only once. The same works down the columns. So the missing cell holds every line of the two cells to its left — top, top-right, right, bottom, bottom-left and left (6 lines) — which also equals the two cells above it: (d). (a) wrongly removes the lines the two figures share, (b) misses the bottom-left line, and (c) has all 8 lines.