A geologist collects a rock sample that has large, well-developed grains surrounded by smaller grains

What type of rock is the sample?

A) porphyritic, extrusive igneous
B) Foliated, regional metamorphic
C) intrusive igneous
D) detrital sedimentary

This is a really poorly worded question and terrible selection for answers.

An argument could be made for any of the answers. But because the question refers to grains instead of crystals, my guess is that it is sedimentary. Probably a sandy conglomerate.

However, the term "well developed" makes me think crystals. A metamorphic schist with "well developed" garnet crystals would fit the bill too.

And of course a porphyritic basalt with phenocrysts of feldspars would work as well.

Even an intrusive rock like granite would work.

Good luck. Who ever made up that question should take a geology class.