HELP BIO PAPER 6 QUESTION

[Hiba Alkindi]

Hi , does anyone know how to solve question 2 b (I) http://www.xtremepapers.com/CIE/Cambridge IGCSE/0610 - Biology/0610_s11_qp_62.pdf
I have my exam tmrw

 

[Gimmick]

I was just doing that same paper! Although this was a good question, the answer was easily found...in the marking scheme
More specifically, this:

 

[Mr haytham]

usually in questions like this, it is better to follow the procedure: count the number of squares filled or filled more than half as filled and the ones filled less will be ignored