attention grammarians!

[nolly]

"This index will show you the number and percent of students that selected specific answer options."

OR

"This index will show you the number and percent of students who selected specific answer options."

OR

something else?

Comments

[arielblue.livejournal.com]

You could also avoid the problem entirely by saying
"This index will show you the number and percent of students selecting specific answer options."