Which of the following statements regarding enzyme regulation is true?

A) addition of an inhibitor to a V system results in kinetics similar to addition of a competitive inhibitor to a typical hyperbolic system
B) allosteric effectors are always more powerful than covalent modification
C) addition of an allosteric activator to a K system changes the plot of V vs. [S] from a sigmoidal curve to a more hyperbolic curve
D) the T state of an enzyme generally has more activity than the R state
E) none of the above are true