There are n airports which form a regular n-gon. In the beginnig, there is exactly one plane at only k airports. Each of the planes flies to one of the nearest airport each day. For which of the following ordered pairs (n,k), it is impossible to gather all planes at a airport on one day however the planes are arranged initially?<spanclass=′latex−bold′>(A)</span>(10,6)<spanclass=′latex−bold′>(B)</span>(10,4)<spanclass=′latex−bold′>(C)</span>(11,3)<spanclass=′latex−bold′>(D)</span>(11,5)<spanclass=′latex−bold′>(E)</span>(13,8)