Which type of rock did the geologist most likely find? gneiss
marble
slate
quartzite

You didn't provide a lot of information so I did some research on your question. If this context looks right then this is the answer! :D

Question that I think you got:

"A geologist finds a metamorphic rock and notices that it has grains that formed in parallel layers. The geologist pries at the rock, and it splits apart along the bands formed by the layers.

Which type of rock did the geologist most likely find?  

gneiss

limestone

marble

sandstone"

Gneiss

Explanation:  

Metamorphic rocks are classified based on their grain arrangement into foliated rocks and non-foliated rocks. These foliated rocks are the ones in which the grains are arranged in parallel layers bands which allows them to   split apart along these band. Some common examples of foliated metamorphic rocks are slate, schist, and gneiss which gives us our answer of geniss. (some of the answer from "podgorica" on )

Gneiss

Explanation: Metamorphic rocks are classified based on their grain arrangement in to  foliated rocks and non- foliated rocks. The grains are arranged in parallel layers bands which allows them to split apart along these band.