**Answer:**

The correct answer is **A) IP (Internet Protocol)**.

**Explanation:**

**1. Internet Protocol (IP):**
IP stands for Internet Protocol. It is a network layer protocol that provides a common address space and routes the packets of data across the entire internet. It is responsible for delivering data packets from the source host to the destination host based on the IP addresses assigned to each host.

**2. Common Address Space:**
IP provides a common address space by assigning a unique IP address to each device connected to the internet. An IP address is a numerical label assigned to each device, and it serves as the device's identity on the internet. It consists of two parts - network address and host address. The network address identifies the network to which the device belongs, and the host address identifies the specific device within that network.

**3. Routing of Data Packets:**
IP also routes the packets of data across the entire internet. When a device wants to send data to another device on the internet, it divides the data into smaller chunks called packets. Each packet is then encapsulated with the necessary information, including the source and destination IP addresses.

The source device sends the packets to its default gateway, which is a device responsible for forwarding the packets to the appropriate destination. The default gateway examines the destination IP address of each packet and determines the next hop on the route towards the destination. It forwards the packets to the next hop, and this process continues until the packets reach the destination device.

**Conclusion:**
In summary, IP is the protocol that provides a common address space by assigning unique IP addresses to devices and routes the packets of data across the entire internet based on these IP addresses. It ensures that data packets are delivered to the correct destination by following the appropriate routing paths.