Liquids: a) must be contained to stay in one spot b) have a variable volume, but a fixed mass c) are usually more dense than solids and gases d) cannot be changed into gases

B) have a variable volume, but a fixed mass

Explanation:

Option A in incorrect. Liquids have flow.  

Option B is correct. Liquids take the shape of the container in which they are kept, so they have a variable volume. Liquids have a fixed mass as mass is the amount of matter in a substance.  

Option C is incorrect. Liquids are less dense than solids but more dense than gases.  

Option D is incorrect. Liquids can change into gases by a process known as vaporization.