According to the principle of cross-cutting relationships, if an igneous intrusion cuts across a layer of schist, the igneous intrusion is than the schist.
a. more dense than
b. older than
c. younger than
d. the same geologic age as

It would be C! younger than! (:
to give you more background on the Schist (which a lot of people don't quite know what it is) it's a metamorphic rock! They can easily and commonly be split into layers, and they have little course grains! (:
I hope all is well, and you pass! good luck, rockstar! I wish you the best!

B.a pop up at ion changes in response to a change in the environment.