Aggression. Hard civility is often aggressing and the action of sneering is also.
It should read COMPLIMENTARY ADMISSION FOR TEACHERS AND STUDENTS in other words it means that for teachers and students admission is free or "compliments of the house" as the saying goes. Complementary means on the contrary that the teachers and students complement or support each other.
Sentence 3 is the answer because it shows specific evidence. While the other sentences just make claims, 3 is used to support sentence 1’s claim.
