Research Comparing the Level of Customer Behavior and the Level

Research comparing the level of customer behavior and the level of gift given indicated:

A) no relationship between the two.
B) greater re-purchases from customers receiving the more expensive gift.
C) reduced re-purchases from any customer who received a gift in response to pressure to be objective in purchasing decisions.
D) any gift generated re-purchases.
E) all of the above were found to be true