Directions：For each blank in the following passage there are four words or phrases marked A，B，C and D．Fill in each blank with the word or phrase that best fits the context．
Radio began as a point-to-point communication device．In 1919，Radio Corporation of American would charge a fee if you sent a message from one radio to another．Either the senders or the recipients pay the fee．The purpose was basically to undercut the telegraph，and they made their money（51）___，not by providing radio as a （52）___ but by selling hardware．
In about 1922，radio （53）___ into a broadcast mechanism．For broadcasting，in the simple sense，there was a（54）___ and it broadcast，and lots of people could hear it．But broadcasting was seen as a way to drive business to the radio hardware makers．The stations were（55）___ by people who made radios or （56）___，by churches and universities that wanted to get their（57）___ out but weren't going to make money．
And there was a lot of stuff which sounds very （58）___ today about how this medium was going to（59）___．And in the 20s，Radio Broadcast Magazine （60）___ a $500prize for the best essay that answered the question："Who is going to pay for broadcasting，and how？"The winner suggested a （61）___ on radio listeners．Now，it sounds a little strange to us，but that's actually the British model．The BBC supports itself by a tax on TV and radio sets．
There was some discussion about（62）___，and Herbert Hoover，the Secretary of Commerce then，was strongly against this idea．He said it was （63）___ that we should allow so great a possibility for service （64）___ by advertising chatter．The Commerce Department was（65）___ radio at the time．After the creation of national radio networks then the pressure-advertisers wanted to go on with it，people who owned the radio network wanted to sell ads，and that's how radio developed as an advertising medium．