It is generally thought to be of necessity to a college student that he（）(know) at least one foreign language.

A．information should be changed into electronic signals
B．electronic signals should be changed into information
C．the signals should be transmitted by means of media such as telephone wires or radio waves
D．it should provide the key medium for information and signals

A．if you want to contact with Roma, you will pollute it
B．if you try to get familiar with Roma, you will be polluted
C．Roma stresses the sacredness of its own culture and oppose to the outside culture
D．Roma stresses the sacredness of the outside culture and oppose to its own culture