Reading Section Part C : Question 1

Communication is said to be an essential factor in order for Homo Sapiens to be called human. People would probably never have come this far in civilization if some method of communication had never appeared.
 However, though human beings have been communicating with one another for thousands of years, few of our modern methods of communication were possible until the invention of electricity. Writing and delivering letters had been the dominant way to convey messages in interpersonal relationships until the telephone, fax and recently e-mail came into the picture.
 Is postal mail fading away as the newly-developed methods prevail with their easier and quicker features? Many people feel that the traditional post office that we have all grown up to know will soon be a quaint old memory of a distant age. Statistics from Japan's Ministry of Postal Services, however, show that the volume of traditional mail was growing steadily even in the 1990s, when pagers, cell phones, and the Internet became social phenomena.The number of letters and parcels sent per person each year almost reached 200 in 1995, an increase of 8% since 1990. Although this figure includes commercial mail sent by businesses, it cannot be denied that postal mail is still very much alive and well.
 Among the four categories of postal mail, letters, postcards, New Year's postcards, and parcels, letters have been ranked at the top since 1988, exceeding postcards, which had been at the top until then.
Postal mail is preferred because it gives a polite and sincere impression to the recipients. According to a report, almost 50% of people pointed out that writing a letter is more polite and more than 40% said they feel the sincerity of the sender when receiving a letter. And the top reasons for choosing letters as a tool of person-to-person communication was that letters express a person's feelings well, which was confirmed by about 56% of the people in the survey.
 In spite of the prevalence of the telephone, fax and e-mail, postal mail is still the major means of communication. It is still used by people who want to convey their messages sincerely and securely. According to the author, our modern methods of communication have been made possible on account of what invention?

According to the author, our modern methods of communication have been made possible on account of what invention?