http://onlinestatbook.com/2/graphing_distributions/line_graphsM.html
here's the link to your image.
http://i.imgur.com/l27Jz4b.png
basically, you're connecting the midpoint at the top of each bar together.
based on that, your selection appears to be selection B as shown below.
the reason is that you are connecting the midpoint of each bar.
the midpoint of each range and the value at that midpoint is shown in the following table:
date range midpoint (x-value) value (y-value) 10 to 14 12 2 15 to 19 17 5 20 to 24 22 13 25 to 29 27 17 30 to 34 32 6
this agrees with the (x,y) coordinates shown on the graph.