Imagine that 1 milliliter of an experimental drug diluted in a saline solution is injected into 20 pregnant mice to determine possible side effects. Which of the following is a suitable control for this experiment?

A) 20 pregnant mice injected with 2 milliliters of the drug
B) 20 non- pregnant mice injected with 1 milliliter of the drug
C) 20 male mice injected with 1 milliliter of the drug
D) 20 pregnant mice injected with 1 milliliter of saline
E) 20 male mice injected with 1 milliliter of saline