Question 51 gives you something practical: a text message, a notice, an invitation, or a short letter between two people who know each other. Question 52 gives you a more descriptive or informational passage, closer to something you'd read in an article. Both ask the same core skill: figure out what the missing sentence needs to do, then write it in a way that matches the register of the rest of the text. If the letter uses casual polite endings like 어요, your blank shouldn't suddenly switch to formal 습니다, and the reverse is just as noticeable to a grader. Question 52's informational passages often use a third register instead, the plain written style ending in 다 (like 성장한다 or 성장할 것이다), which needs its own separate check since neither 어요 nor 습니다 belongs there.