In this passage, "optical" can be understood as related to ______.

单项选择题The most appropriate title for the passage could be ______.

单项选择题We get the impression that the author seems to be ______. Hardy's impulses as a writer.

单项选择题According to the passage, ______ has become the driving force for the development of telephone system

单项选择题Which of the aspects of telecommunication is NOT mentioned in the passage

单项选择题Television is a ______ in the transmission of message.