"why don't you just be quiet? " vince growled at nate.
"you aren't in charge here! you think you are the big man
on campus, but you're not anymore. i've been trying to
ignore you all semester, but not anymore. i've had it."
vince balled his fists, and nate straightened to look
larger.
which most likely explains why the author uses expressions like "growled,"
"balled his fists," and "straightened to look larger" to describe the characters?

a. to reveal that vince is the antagonist and nate is the protagonist
b. to show that vince and nate are old friends who are now arguing
c. to prove that the two boys are both in the wrong and should
apologize
d. to show that the tension is rising between the two characters