Quiz: Efficient Comparison Sorts

QuickSort has $O(n^2)$ worst case but is often faster than merge sort in practice. Why?

1. A.QuickSort uses less memory since it sorts in place
2. B.QuickSort has better cache locality and lower constant factors
3. C.QuickSort's worst case rarely happens with random data
4. D.All of the above contribute to QuickSort's practical speed