It is the firm belief of astronomers that there are living creatures on other planets. It

is also their earnest wish that some day contact may be made【C1】______such living creatures by sending messages with the help of radio signals. The【C2】______of communicating with people on other planets may one day come true since radio telescopes have now been invented. Scientific projects of various kinds are now being launched to【C3】______signals or to receive signals from distant planets. The question now【C4】______. What sort of message should be sent so that it could be understood. To send a message in any language would be impractical as it would【C5】______not be intelligible.【C6】______is the opinion of scientists that a signal in the form. of a simple arithmetic sequence might be understood. Scientists think that pictures might also be understood, so it would be a good idea to send pictures of the people【C7】______our planet. Pictures of domestic animals together with various crops we【C8】______for our food might also be sent. Pictures of houses and buildings might【C9】______further information about our life and society. As time goes on, TV pictures might be sent which would make the beings on other planets aware【C10】______the life and the level of civilization on our planet.

【C1】

A．with

B．upon

C．by

D．to