Paxton Owns a Swimming Pool, and Last Summer He Got

Multiple Choice

Paxton owns a swimming pool, and last summer he got some yellowish algae in the water. He bought a specific type of algaecide to deal with the problem and in three days, the water was clear again. This summer Paxton notices a green algae beginning to form, and he uses the same algaecide as he did the previous summer. In three days, the pool is completely green and he cannot determine why the algae didn't die. Paxton failed to realize that it was a different type of algae, and his use of a past solution attempt demonstrates

A) a mental set.
B) functional fixedness.
C) the availability heuristic.
D) a failure to consider negative evidence.