Which of the following is the best example of derepression?

A) Switching on of the trp operon in the presence of tryptophan
B) Switching off of the trp operon in the presence of tryptophan
C) Switching off of the trp operon in the absence of tryptophan
D) Switching off of the lac operon by the presence of glucose in the medium
E) Switching on of the lac operon in the presence of lactose