If the coast guard warns of a giant wave of water approaching the shore as a result of a major earthquake, they are warning of
a. an aftershock.
b. liquefaction.
c. a tsunami.
d. landslides.

C. A Tsunami

Explanation:

When there are earthquakes, volcanic eruptions or some underwater disturbances, a hue amount of water is displaced in the form of huge waves in a sea. This is known as tsunami.

In 2004 a major tsunami was caused by an undersea earthquake, in Indian Ocean, resulting in waves as high as 30 meters and affected 15 countries. Indonesia, Sri Lanka, and India were the worst affected countries.

gas and liquid