Answer the following question given this paragraph: 

In this reaction, and are positively-charged cations, while and are negatively-charged anions. Double-replacement reactions generally occur between substances in aqueous solution. In order for a reaction to occur, one of the products is usually a solid precipitate, a gas, or a molecular compound such as water.


Q: Double-replacement reactions generally occur between substances in what kind of solution?

 Choices:

- solid

- reactive

- saline

- aqueous

A:
aqueous
