Under Which of These Circumstances Is Synergism Occurring

Under which of these circumstances is synergism occurring

A) when one hormone induces the loss of another hormone's receptors
B) when the actions of several hormones are complementary, and their combined effect is greater than the sum of their separate effects
C) when one hormone must be present in adequate amounts for the full exertion of another hormone's effect
D) when one hormone increases the number of target-tissue receptors for another hormone