Question

most of the rocks we study were formed in what era?
a. precambrian
b. paleozoic
c. cenozoic
d. mesozoic

Explanation:

To determine the era when most studied rocks were formed, we recall geological time scales. The Precambrian era spans about 88% of Earth's history and saw the formation of many ancient rock formations, including igneous, metamorphic, and early sedimentary rocks. The other eras (Paleozoic, Mesozoic, Cenozoic) are much shorter in duration and account for a smaller portion of rock formation relative to the Precambrian.

Answer:

A. Precambrian