Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions.

A. Before the invention of newspapers, the main source of news was word of mouth. Any writings and drawings were done by hand. Although printing presses had existed in eastern Asia, it was Gutenberg's invention in Europe in 1453 that made printing faster and books more accessible. It reduced the cost and size of printed books and made them the first form of mass media affordable to less wealthy people. Gufenberg's invention also quickened the spread of discoveries and information, and promoted literacy in Europe.

B. The printing press led to the rise of printed newspapers that appeared regularly. The first newspapers developed from around 1612 and in a short period of time, they became very popular in Europe and the European colonies. In the 19th century, they also appeared in Asia. Newspapers and magazines are still very popular today. Although most of them have online versions, many people continue to read print media, which is considered more credible than digital media.

C. In the 1920s, when radio, television, and video were introduced, the phrase 'the media' began to be used. Black and white television quickly became popular in the 1950s, and in the 1960s colour broadcasts started in many countries. Thanks to its audio visual presentation, television became one of the most important forms of mass media in the 20th century. As a source of news, entertainment, and education, it still attracts a large number of viewers today.

What is the main idea of Paragraph A?