Which of the following might account for the variations in maximal jaw angle? (A) Different wind speeds

Question:

Which of the following might account for the variations in maximal jaw angle?
(A) Different wind speeds on each island
(B) Different heights of trees on each island
(C) Different sizes of seeds on each island
(D) Differences in altitude on each island

A chain of three small islands was found to be the home to a small species of mouse. The angle of jaw opening was found to vary significantly. The average size angle of the maximal jaw opening found in mice at 10 locations on the three small islands is shown in Figure 1, below. Island A A1: 22 A2: 21 A3: 22 Island B B4: 32 B1: 31 Island C B3: 32 B2: 34 C1:219 3: 21 C2: 21