Given the question: Answer the following question given this paragraph: Animals may eat and drink at certain times of day as well. Humans have daily cycles of behavior, too. Most people start to get sleepy after dark and have a hard time sleeping when it is light outside. Daily cycles of behavior are called circadian rhythms . Q: What is the term for daily cycles of behavior, like the sleep-wake cycle? Choices: - daily rhythms - variable rhythms - behavioral rhythms - circadian rhythms A:
The answer is:
circadian rhythms