C option, the linear function corresponds to a constant, such as y= 1, which is not increasing function, so it is excluded.

F'(x) in a? b？ There are three situations in the world. First, the right side of a begins to increase, that is, F(a) is greater than 0.

Second, the single station image passes through the middle of ab, that is, F(a)x? F(b) is less than zero.

Third, the single station image passes through the right side of B.

Draw the original function and find the a option.