Assertion. There is a difference between a standalone computer and a computer as a network node.

Reason. A standalone computer needs a special hardware NIC to be a network node.

(a)

Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

Explanation
A standalone computer operates independently without being connected to a network, while a computer serving as a network node participates in network communication. To function as a network node, a computer requires a Network Interface Card (NIC) hardware, which facilitates communication over the network.