Which of the following statements about B-trees and B+ trees is correct?

1. A.

   B-trees are for storing data on disk and B+ trees are for main memory.

2. B.

   Range queries are faster on B+ trees.

3. C.

   B-trees are for primary indexes and B+ trees are for secondary indexes.

4. D.

   The height of a B+ tree is independent of the number of records.

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