In Relation to the Therapeutic Window of a Drug, Which

In relation to the therapeutic window of a drug, which of the following sentences is true:

A) Drugs with wide therapeutic range are not potent enough compared with narrow therapeutic range.
B) A drug must exceed the maximum effective dose in order to be therapeutically active.
C) Drugs with plasma concentration below the minimum effective concentration show no therapeutic effect.
D) It is a range of concentration that determines both the safety and efficacy of drugs.