Which type of pronoun is used in the following sentence? mars, which is sometimes called the red planet, is the fourth planet in the solar system. interrogative indefinite relative demonstrative

The type of pronoun used in the above sentence is a RELATIVE PRONOUN.

The relative pronoun is found in the beginning of the adjective phrase. The adjective phrase describes the noun.

In the above sentence the adjective phrase is: WHICH IS SOMETIMES CALLED THE RED PLANET.

It describes the noun MARS.

The relative pronoun used is WHICH.