Step 1: Recall the history of the Internet.
The precursor to the modern Internet was a project funded by the U.S. Department of Defense's Advanced Research Projects Agency (ARPA).
Step 2: Identify the network's name.
This network was called the ARPANET. It was the first to implement the TCP/IP protocol suite and is widely considered the first large-scale, general-purpose computer network. NSFNET came later and formed the backbone of the Internet in the late 80s and early 90s.