41.Vowels are formed mainly by the position of the tongue and,secondarily,by the shape of the lips and movement of the jaw.

42.Consonants vary depending on where and how the air stream gets through,the place and movement of the tongue,and also whether the voice is used or not.

43.A phoneme is the smallest distinctive sound unit,incapable of change in different phonetic environments.

44.The back-chaining technique means the students repeat a sentence after the teacher,starting from the end part of the sentence and moving towards the beginning.

45.Of the two types of sentence stress,sense stress shows contrast,while logical stress shows meaning.

46.Pitch is produced by frequency of vibration of the vocal cords.The higher the frequency,the higher the pitch.

47.Usually low key is used for emphasis and contrast;mid key indicates an expected,neutral attitude;and low key provides low information.

48.Of the four possible tune movements,high fall is used for statements and wh-questions;high rise is used for questions asking for repetition of something;low rise is for yes/no questions,etc.and fall rise is for corrections and polite contradictions.

49.The most powerful signal of stress is a change of pitch on the vowel.

50.Syllables are short when they are stressed.