You are given a science question (hard-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.
Q: Robots can perform tasks that are dangerous for humans. What is the MAJOR limitation to the use of robots?
(A) The assembly pieces must be very small. (B) The assembly process must remain exactly the same. (C) Robots require regular maintenance. (D) Robots must be provided with electricity.
A:
B