Final answer:
Maria's behavior is being maintained by c. negative reinforcement by escape.
Step-by-step explanation:
Maria's behavior is being maintained by negative reinforcement by escape. Negative reinforcement occurs when a behavior is strengthened by the removal or avoidance of an aversive stimulus. In this case, Maria quickly unplugs her computer equipment when she sees lightning to avoid potential damage from an electrical surge. By removing the aversive stimulus (the risk of damage), her behavior of unplugging the equipment is reinforced and more likely to be repeated in the future.