Which of the following is true about a red-black tree?

I'm sorry, but you didn't provide any options for the question about the red-black tree. However, I can tell you some true facts about a red-black tree:

1. A red-black tree is a kind of self-balancing binary search tree in computer science.
2. Each node in the binary tree has an extra bit for denoting the color of the node, either red or black.
3. A red-black tree satisfies the following properties:
   • Every node is either red or black.
   • The root is black. This rule is sometimes omitted. Since the root can always be changed from red to black, but not necessarily vice versa, this rule has little effect on analysis.
   • All leaves (NIL) are black.
   • If a node is red, then both its children are black.
   • Every path from a given node to any of its descendant NIL nodes contains the same number of black nodes.
4. The longest possible path from the root to a leaf is no more than twice as long as the shortest possible path. The result is that the tree is roughly height-balanced.
5. Insertion, deletion, and searching operations run in O(log n) time in a red-black tree.