Answer the following question given this paragraph: 

The surface tension of water is illustrated by a number of common occurrences. For example, water spiders are able to walk across bodies of water because of surface tension. Even though the spiders are denser than water, they do not sink, because the small amount of weight pressing down on the surface is not enough to break the strong hydrogen bonds that hold the surface together.


Q: The ability of a water spider to walk across a body of water is an example of what?

 Choices:

- high density

- low gravity

- magnetism

- surface tension

A:
surface tension
