Which formula is used to measure accuracy?

You can only find REaccuracy if you know the actual “true” measurement… something that's difficult to do unless you're measuring against the atomic clock. The formula is: REaccuracy = (Absolute error / “True” value) * 100%.

Explanation:

given the options, i would say your best bet is c. the modem supports up to 56 kbps, which is too low for video streaming. dial up modems use actual phone lines, which only can go up to 56 kbps as that's more than sufficient for traditional phone calls. this is also the reason why when a dial-up modem connects, you hear all those sounds. it's literally using the phone line to establish a connection.