Mother asked her if she knew where her father had kept the gardening tools after the two of them did some gardening together on sunday. this question from her mother is likely to initiate a process called retrieval in karen's memory

The answer is retrieval
retrieval refers to your ability to access a certain information when you need it.
According to studies, one of the most effective method to improve our ability to memorize something lies within the enhancement of our retrieval processing. This could be done by developing effective cues as trigger that help us to associate that cues with the actual memory.