With this type of question it is all a matter of accuracy.
Looking at the right hand edge of your graph, you do not appear to have made an accurate job of parallelling the spaces between the sloping lines.
I zoomed in to your graph until the gap between the lines at the right hand edge was 31 mm, I then measured the gap between the left hand (lower) end of these lines and it was 16 mm.
At the right hand edge I also measured the gap between your red line and the next sloping line up. This gap was 5 mm.
Parallelling accurately between these lines would get the following
16 mm / 31 mm = X mm / 5 mm
Rearranging this gives X mm = ( 16 x 5 ) mm / 31 mm = 2.58 mm
This means that in the zoomed in condition described above, the left hand end of your red line should be 2.58 mm below the next sloping line up. Measuring it on my computer screen gave me something more like 4 mm.
So you sloping red line is sloping down too much.
Also at the left end of the wind area you appear to have dropped down slightly from your upward lsoping line before drawing your hohizontal line to the left.
These two error would put you too low when moving into the centre of the graph.
These are small errors but the slope of the curevd line sin the centre of the graph is very shallow. The difference between 3430 and 3530 is only a vertical distance of 1 small square on the graph.
As other posters have said, there should be a reasonable distance between each of the options in the questions. But you should also do the best that you can to be accurate in using the graphs.