Vera Thinks That Having Pets Increases Psychological Functioning and Well-Being

Vera thinks that having pets increases psychological functioning and well-being. To test this, individuals in one group of randomly selected nursing home residents are each given a pet while participants in a second group are not given pets. Over two months, the overall level of psychological functioning is evaluated on a daily basis. What is the independent variable in this study?

A) Having pets increases psychological functioning
B) Whether or not the resident received a pet
C) The level of psychological functioning demonstrated by the residents
D) This is a correlational study, so there is no independent variable