A

 Ever since humans have lived on the earth, they have made use of various forms of communication． Generally, this expression of thoughts and feelings has been in the form of oral speech． When there is a language barrier(障碍) communication is completed through sign language in which motions stand for letters, words, and ideas． Tourists and the local people unable to make themselves understood by each other through speaking or writing have had to turn to this form of expressing．Many of these symbols of whole words are very lively and exact and can be used internationally; spelling, however, cannot compare with them．