Sedimentary rock layer b exists between two other layers of sedimentary rock, layers a and c. the ordering of layers a and c has not been altered since disposition, and the layers have not been overturned. base on this information, what can be concluded with certainty?

The information presented indicates that C is the oldest layer; it was deposited first. Layer B is above C so it is younger than C. Layer A is the last to be deposited so it is the youngest of the three layers.
Tectonic forces can sometimes disturb the natural order in which rocks have been deposited; they can be uplifted and overturned. When rock layers have been disturbed over time and does not show the correct sequence of deposition, it is known as an unconformity.

It's lithogenous i believe of course i looked it up.