Refer to the Graph Below

Refer to the graph below. The graph shows data collected using a purified sample of the enzyme phosphofructokinase (PFK) .This enzyme catalyzes the reaction between fructose 6-phosphate and ATP to form fructose 1,6-bisphosphate.Which statement is consistent with the data shown in the graph?

A) PFK is allosterically inhibited by ATP.
B) PFK is allosterically activated by ATP.
C) ATP is a competitive inhibitor of PFK.
D) ATP functions as a substrate and not as an inhibitor of PFK.
E) ATP functions as a substrate and not as an activator of PFK.