Под каким напряжением работает рентгеновская трубка, если самые «жесткие» лучи в рентгеновском спектре этой трубки имеют частоту 1019 Гц?

Put in prepositions if needed: of, in, - , to, with, by, with, - ,Put in prepositions if needed: of, in, - , to, with, by, with, - , in. 
About ten years ago telephone was the only means of communication which people could use (in) their home (-) present computers make our life much more comfortable. Now we can send messages (to) each other (by) fax, e-mail or communicate (with) the internet. Those who have the internet can communicate not only (with) people. They can get (-) information (of) any library all over the world.