You are given a sentence, a question and two answer options ('A' and 'B'). Your task is to find the correct answer (return the string of the correct option, not 'A' or 'B') for the given question.
Q: Sentence: One of Sarah's neighbors spilled dog food all over the stairs. The dog food pieces are on three stairways and all over the landings. Sarah gets mad and kicks a piece of dog food. The dog food flies across the wooden planks from one side of the staircase landing to the other. The dog food reaches the neighbor's door mat. It moves a few inches across the doormat. Question: Why didn't the dog food move further across the doormat? (A) The door mat is a spikier surface (B) the staircase landing is a spikier surface
A: 
The door mat is a spikier surface