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

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

请帮忙给出正确答案和分析，谢谢！