Circle O has diameters AB and CD perpendicular to each other. AM is any chord intersecting CD at P. Then AP⋅AM is equal to:
[asy]defaultpen(linewidth(.8pt));
unitsize(2cm);
pair O = origin;
pair A = (-1,0);
pair B = (1,0);
pair C = (0,1);
pair D = (0,-1);
pair M = dir(45);
pair P = intersectionpoint(O--C,A--M);draw(Circle(O,1));
draw(A--B);
draw(C--D);
draw(A--M);label("A",A,W);
label("B",B,E);
label("C",C,N);
label("D",D,S);
label("M",M,NE);
label("O",O,NE);
label("P",P,NW);[/asy]<spanclass=′latex−bold′>(A)</span>AO⋅OB<spanclass=′latex−bold′>(B)</span>AO⋅AB<spanclass=′latex−bold′>(C)</span>CP⋅CD<spanclass=′latex−bold′>(D)</span>CP⋅PD<spanclass=′latex−bold′>(E)</span>CO⋅OP