Techniques for grouping items of vocabulary fall into three general categories: semantic fields, phonological sets and grammatical sets. Grouping items related by topics, for example, types of fruit, belongs to the semantic fields.（）

判断题Syllables are short when they are stressed.（）

判断题The most powerful signal of stress is a change of pitch on the vowel.（）

判断题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.（）

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

判断题Pitch is produced by frequency of vibration of the vocal cords. The higher the frequency, the higher the pitch.（）