Answer:
choice a. between x=0 and x=1
Explanation:
The question says when is it INCREASING the fastest. So you don't consider the horizontal portion or the negative slope portions of the graph.
Find which section of the graph with the greatest positive slope (steepest) and that is
0 ≤ x ≤ 1
First section of the graph has a slope of 2, the next has a slope of 1