Which one of the following features can control left and right indents on using markers

Hey i just logged on and one of the moderators deleted a bunch of my answers to questions, even though the answers were right and the people it doesn't make sense but if anyone wants to talk about anything just message me lol (this is super random lol)

Suppose there is a relation r(a, b, c) with a b+-tree index with search keys (a, b).1. what is the worst-case cost of finding records satisfying 10 < a < 50 using this index, in terms of the number of records n1, retrieved and the height h of the tree? 2. what is the worst-case cost of finding records satisfying 10 < a < 50 and 5 < b < 10 using this index, in terms of the number of records n2 that satisfy this selection, as well as n1 and h defined above? 3. under what conditions on n1 and n2, would the index be an efficient way of finding records satisfying the condition from part (2)?

Which of the following is not a “fatal four” event?