Given the task definition and input, reply with output. Given a scientific passage and an answer, generate a question for the given answer.

Passage: The properties of cyclic hydrocarbons are generally quite similar to those of the corresponding open-chain compounds. So cycloalkanes (with the exception of cyclopropane, which has a highly strained ring) act very much like noncyclic alkanes. Cyclic structures containing five or six carbon atoms, such as cyclopentane and cyclohexane, are particularly stable. We will see in Chapter 16 "Carbohydrates" that some carbohydrates (sugars) form five- or six-membered rings in solution. Answer: stable
The properties of cyclic hydrocarbons are generally quite similar to those of the corresponding open-chain compounds. so cycloalkanes (with the exception of cyclopropane, which has a highly strained ring) act very much like noncyclic alkanes. cyclic structures containing five or six carbon atoms, such as cyclopentane and cyclohexane, are particularly what?