The pentagon changes its size and its colour, but the two changes do not repeat at the same rate. Which pentagon comes next?

The size simply alternates: big, small, big, small, big, so the next is small. The colour repeats in a cycle of three: orange, blue, yellow, orange, blue, so the next is yellow. A small yellow pentagon: (c). (a) is the right colour but big, (b) restarts the colours too early and (d) repeats blue.