The correct option is C the
Sometimes we generalize nouns by using 'the' with a singular countable noun, like with the names of scientific inventions like the 'telephone'. Hence the option C is correct. The articles 'a' and 'an' are used for nouns which are not specific, over here we're not talking about any telephone, but the very first telephone which was invented, hence these options are incorrect. Since 'telephone' is a countable noun and a specific one, the option D is also incorrect because we are referring to a specific telephone i.e. the first one.