Answer:
D: one of the non-fiction books on the bottom shelf and a second non-fiction book from the bottom shelf
Explanation:
A pair of 2 dependent events are simply those in which the choice of the second item depends on taking the first item such that the probability changes.
Because when the first item is taken without replacement, the sample size would have reduced and as such picking the exact same item will reduce the probability.
Now, what this means in relation to the question is that for 2 of the events to be independent, they must be on the same shelf and of same type of book such that the second book can't be selected until the first one has been selected.
The only option that fits this definition is option D where both books are on the same shelf and they are same type of books.