[Solution 1]
Since it is a multiple-choice question, the better way is to draw pictures.
F'(x)>0 = & gtF(x) increases.
F''(x)>0 = & gtF(x) increases in a concave shape.
It can be seen from the figure that to choose a, of course, we must know the geometric meaning of dy and △ y.
The increment of dy tangent, and △y is the increment of function.
[Solution 2]
Properties of concave function;
F(x0+△x)>F(x0)+f'(x0)△x (△x is not equal to 0)
That is, f (x0+△ x)-f (x0) >: f' (x0) △ x >; 0(△x & gt； 0)
That is △ y > dy & gt0