Read the following paragraph carefully and choose the best topic sentence from the four possible answers that follow the paragraph by writing A, B, C or D.
Topic Sentence:__________
A few years ago, letter writing was the most important means of communication and people seldom made phone calls, especially in the rural areas, because there were not many telephones available. With the rapid development of China's economy, telecommunication service is badly needed. For example, when many young Chinese go abroad to work or to study, they want to get in touch with their folks regularly and easily. Private companies have mushroomed all over China; businessmen realize the importance of telephone. In the countryside, letters usually take several days or weeks, and much time will be wasted, so people have dreamed for many years to have telephone service. Since many families are getting rich, they can afford it now.
A. Nowadays, more and more people rely heavily on the telephone instead of letters.
B. Nowadays letter writing is the most important means of communication.
C. Internet is the most important means of communication today.
D. Many families in China are getting rich now.