George Dropped His Keys into a Grate on the Sidewalk

Multiple Choice

George dropped his keys into a grate on the sidewalk in front of his house. He could see them, but couldn't reach them. He went back into his house and noticed that his son was using the vacuum cleaner to pick up some cereal that was spilled on the floor. This gave George the idea to put the long hose of the vacuum into the grate to pick up the keys. This sort of thinking relies on which of the following?

A) mental set
B) functional fixedness
C) algorithms
D) analogies