We're just going to want to draw this one. Start by drawing 6 points, no 3 of which lie on the same line (a good idea is to put them roughly in circular shape):
Now just start connecting them with lines (counting as you go, making sure not to miss any). Start by going around the outside:
That's 6 lines. Now connect everything else through the middle (remember to COUNT AS YOU GO):
It's confusing to count them all up afterwards, which is why you need to count as you go. If you were careful, you counted 9 more.
That's a total of 6 + 9 = 15. (A) is our answer.