Question

the arpanet was a 1960s prototype computer. a 1960s computer company. a 1960s university email system. a 1960s government computer network.

Explanation:

The ARPANET was developed by the U.S. Department of Defense's Advanced Research Projects Agency (ARPA) in the 1960s. It was a network that connected computers at various research institutions. It was not a single computer (so not a prototype computer), not a company (as it was a network infrastructure), and not just a university - specific email system (though email was later developed on it). It was a government - funded (by ARPA, a government agency) computer network.

Answer:

a 1960s government computer network.