If you're trying to decide whether you actually bought milk,or whether you just planned to buy milk,which process are you using

A)  reality monitoring 
B)  locus of causality 
C)  source monitoring 
D)  internal or external attribution

Source monitoring refers to the process of determining the origin (source) of a piece of information or memory. In this case, you are trying to remember whether you actually bought milk (source monitoring), as opposed to simply planning to buy milk (which would involve a different type of memory). Reality monitoring (A) would involve distinguishing between real vs. imagined events, locus of causality (B) involves identifying the cause of a particular outcome, and internal/external attribution (D) involves assigning responsibility for an event to oneself or external factors.