What adds the element carbon to the environment?

Climate change happens because of global warming, which is the result of over accumulated Carbon dioxide in the atmosphere trapping the sun’s rays in the earth. This is due to the careless use and disposal of chemicals containing Carbon such as CFCs in the atmosphere.

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.