Answer
a) is correct.
Work Step by Step
We know that $$x_{cg}=\frac{W_1x_1+W_2x_2+...}{W_1+W_2+...}$$
The equation shows that the position of center of gravity depends on the weight of the objects and their positions.
So when fruit grows, there are more weights on the outer end of the branch, shifting the center of gravity toward the pears at the outer end. a) is correct.