"그 책은 다음 섹션에 있다."
번역:That book is in the next section.
Part of the problem with the translations is that in making an effort to teach English, Duolingo has to use unnatural Korean expressions. This can be frustrating, but Korean speakers just need to recognize the fact and work with it. The "articles" "a" and "the" don't really have a common counterpoint in Korean so Duolingo translations will often be a bit awkward. In real life, it is more likely that "그" will translate as "that" rather than "the." because in Korean, there is usually no need for "the." In English it is "Give me the book." In Korean, it is "책 줘."
Philo, English prepositions are difficult. Often "at" ,"on" & "in" can be used in very similar situations. It will take a lot of memory work to keep them all straight because there are exceptions to the rules. Usually when we use "at" it has a connotation of being temporary. We say "He is at work / the library / school / the ball game / lunch." We expect that situation will change within a fairly short period. The books in a section don't usually move around, so that may be why we don't use "at."
"At home" is probably the most common translation for 집에서. He works at home. (as opposed to going to an office)
She is a stay-at-home mom. (She doesn't have a job outside the home, but concentrates on raising the children.)
Restaurants are so expensive that we usually eat at home.
but is also used for 집에
"Is your wife here?"
"No, She's at home."
"Can you pay for lunch? I seem to have left my wallet at home."
We have a garden at home.
Our children are at home.
I'll see you at home.
When "home" is a destination, we don't need a preposition.
I am going home.
It's time to head home.
Will you be home for Christmas?
Sometimes 집 is translated "house." Then it is more common to use the preposition "in."
The dog sleeps in the house. (not outside)
He grows plants in the house.
You can also say "He grows plants at home." but it doesn't have the same connotation. With this sentence, the assumption is the plants are grown in an outside garden.
"What is your wife doing?" (You are talking with a neighbor)
"Oh, she is doing some chores in the house." (It would sound strange to say "at home" since you are right next to your home."