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.
B.
A terrible head wound he suffered in battle.
