Answer the following question given this paragraph: 

A familiar liquid is mercury metal. Mercury is an anomaly. It is the only metal we know of that is liquid at room temperature. Mercury also has an ability to stick to itself (surface tension) – a property all liquids exhibit. Mercury has a relatively high surface tension, which makes it very unique. Here you see mercury in its common liquid form.


Q: What is the only metal that is liquid at room temperature?

 Choices:

- hydrogen

- gas

- water

- mercury

A:
mercury
