The correct answer is the "teach, understand" pair. This question is testing your knowledge of present tense vs. past tense. To find the correct answer, you must read the paragraph as a whole and maintain verb tense consistency. Since the second verb in the first sentence (attend) is in present tense, and the first and third verbs in the third sentence (It's and is) are both in present tense, you can safely assume that the remaining verbs will also be in present tense.
I agree. For example when looking at the Elizabethan Era poets, playwrights, and authors wrote about issues and events that pertained to what was going on during that time. The event shown in their pieces shows people of this generation how people thought during that time and how they handle different situations. The same goes for culture. Looking at work from a generation shows how times have changed and how humans have changed.
D, the first one should be who instead of that, the second one should be that instead of which, the third one should be that instead of which