Which of the following is true about rocks? a) rocks are composed of only one mineral. b) rocks do not contain any nonmineral matter. c) coal is not considered a true rock. d) most rocks are a mixture of minerals.

D). Most rocks are a mixture of minerals

Rocks are the natural substances these are the aggregate of one or more number of minerals. These minerals are responsible for chemical and physical nature of rocks. These are responsible for type of particles, texture of particles and overall rock structure. Example of rock having mineral aggregate is granite which is a combination of minerals like quartz, biotite and feldspar.