(1) The sides of canyons and cliffs can be made of different layers of colored rock or types of rock. (2) These layers are formed by the natural elements. (3) These layers can be made of many types of materials: sand, silt, or lava. (4) Each layer is called a stratum while multiple layers are called strata.

Question

anonymous · Answer

Sentence 4 is an example of a

anonymous · Answer

A. compound-complex sentence.
    B. simple sentence.
    C. compound sentence.
    D. complex sentence.

texaschic101 · Answer

compound sentence. 
Each layer is called a stratum - independent clause
multiple layers are called strata - independent clause
" while"  is the conjunction connecting the two independent clauses.