Which of the following events happened first?

D. ARPANET was created

Explanation:

The correct answer is D because ARPANET was created in October 1969, Web 2.0 was created in 1999, email was invented in 1971, and the world wide web was created in 1989

the answer to your question would be something called hertz. the unit of measurement called a hertz, which is one cycle per second, is used to measure clock speed. within one cycle, your computer processes, refreshes, or updates itself to the changes that it is going through. in the case of computer clock speed, one hertz equals one tick per second. the clock speed of computers is usually measured in megahertz (mhz) or gigahertz (ghz)