Given a scientific question, generate a correct answer to it.

Input: Consider Input: What kind of energy is specifically defined as the energy that is available to do work?

Output: free

Input: Consider Input: Shielding should be used when receiving x-rays to limit exposure to what potentially harmful form of energy?

Output: radiation

Input: Consider Input: What are solutions that maintain a relatively constant ph when an acid or a base is added?
Output: buffer