Which One of the Following Statements Most Accurately Describes Intermittent

Which one of the following statements most accurately describes intermittent reinforcement?

A) The reinforcement a student receives becomes stronger over time.
B) A particular response is reinforced on some occasions but not on others.
C) A primary reinforcer is used at first, but it is gradually replaced by a secondary reinforcer.
D) One response is reinforced for a while, then another response is reinforced, then another, and so on, over a period of several weeks or months.