【正确答案】：
A) PHONETIC FEATURES: IN COMPOUNDS THE WORD STRESS IS ON THE FIRST ELEMENT.
B) SEMANTIC FEATURES: EVERY COMPOUND EXPRESSES A SINGLE IDEA.
C) GRAMMATICAL FEATURES: A COMPOUND TENDS TO PLAY A SINGLE GRAMMATICAL ROLE IN A SENTENCE. 
【题目解析】：a）语音特征：在复合词中，单词重音在第一个元素上。b）语义特征：每个复合词表达一个单一的概念。c）语法特征：复合词往往在句子中扮演单一的语法角色。