What is the most likely explanation for the observation that the blue color ... ...

What is the most likely explanation for the observation that the blue color never disappears at 60° C?
(A) The chemical bonds in starch are stabilized by the heat so that it cannot break down even though the enzyme is highly active.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in 03. Enzymes and Energy