阅读理解 　　Questions 11—15 are based on the following passage: 　　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, communication is completed through sign language in which motions stand for letters, words, and ideas. Tourists and the people unable to hear or speak have had to turn to this form of expression. Many of these symbols of whole words are very lively and exact and can be uesd inerenationally; spelling, however, cannot. 　　Body language sends ideas or thoughts by certain actions, either meaningfully or not. A wink can be a way of showing that the party is only joking. A nod means agreement, while shaking the head indicates disagreement. 　　Other forms of nonlinguistic language can be found in Braille (a system of raised dots read with the fingertips), signal flags, Morse code, and smoke signals. Road maps and picture signs also guide and warn people. While language is the most common form of communication, other systems and techniques also express human thoughts and feelings.

单选题 Which of the following statements best summarizes this passage?

单选题 Which of the following statements in NOT true?

单选题 Which form other than oral speech could be most commonly used among blind people?

单选题 Sign language is said to be very lively and exact and can be used meaningfully except for ______.

单选题 How many different forms of communication are mentioned here?