For most of human history, the primary means of communication across long distances was not the computer, telephone or(36)______

For most of human history, the primary means of communication across long distances was not the computer, telephone or(36)telegraph, but the letter. In the 18th and 19th centuries, letters were the(37)primary source of information on politics, social conditions, and even natural disasters. A series of(38)innovations, including the invention of the pencil in the 18th century and the(39)steady reduction of postal rates in the 19th century,(40)affected not only the length and content of letters, but the(41)frequency with which they were sent. But few developments changed written communication as much as the introduction of a simple product that(42)created a national craze at the turn of the 20th century, the postcard.
    Postcards were first developed in the 1870 s as(43)promotional advertisements for hotels, resorts, and other businesses. In 1906,(44)the United States Congress passed laws allowing messages to be written on one half of the back side of postcards, in effect encouraging people to substitute them for short letters. From that point on,(45)the use of postcards rose steadily from about 770 million that year to almost 1 billion 3 years later. Manufacturers sprang up to meet the demand. By 1909, the Illustrated Postcard Company alone was producing 3 million a day.
    Postcards were more than a means of communication. Like stamps, they became collector’s items to be bought, sold, and traded.(46)Many people used postcards to acknowledge the receipt of letters and to promise a quick response. They also became a means for travelers to update friends and family on how a trip was progressing or to offer a photographic glimpse of their destinations.