Final answer:
Flysch and molasse are sedimentary rock formations that provide geologists with important information about Earth's tectonic history, specifically relating to mountain building and erosion.
Step-by-step explanation:
Flysch and molasse are sedimentary rock formations related to mountain building. They are useful for geologists because they provide information about tectonic history. Flysch is typically associated with the deep marine deposits found in the early stages of mountain building when the crust is being folded and deformed. These deposits are often found in subduction zones, where an oceanic plate is being pushed beneath a continental plate. Molasse consists of terrestrial deposits that form in the later stages of mountain building, usually consisting of sandstones, shales, and conglomerates, which are the result of erosion from rising mountains.
The correct answer to the question "What are flysch and molasse? Why are they useful for geologists?" is d) Sedimentary rock formations related to mountain building; provide information about tectonic history.