With reference to the B+ tree index of order 1 shown below, the minimum number of nodes (including the Root node) that must be fetched in order to satisfy the following query: "Get all records with a search key greater than or equal to 7 and less than 15" is ______.

To retrieve all records with a search key in the range $[7, 15)$:

1. Fetch Root Node containing key [9]: Compare search key $7$ with $9$. Since $7 < 9$, follow the left child pointer. (1st node fetched)

2. Fetch Internal Node containing key [5]: Since $7 \ge 5$, follow the right child pointer. (2nd node fetched)

3. Fetch Leaf Node containing [5, 7]: Key $7$ is found in this leaf node. (3rd node fetched)

4. Follow leaf-level right pointer to Leaf Node[9, 11]: Contains valid keys $9$ and $11$ in the range. (4th node fetched)

5. Follow leaf-level right pointer to Leaf Node[13, 15]: Contains valid key $13$. The key $15$ terminates the search range without needing to fetch the next leaf. (5th node fetched)

Thus, the total number of nodes fetched is $1 + 1 + 1 + 1 + 1 = 5$.