What is the dummy piece of code used during the top-down approach of integration testing

i think it's Stubs and drivers

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.

a.s= 230t– 110; 1500 lbc.t= 230s– 110; 1500 lbb.s= 230t+ 110; 1720 lbd.s= 199t– 110; 1280 lb