阅读下面短文，按照句子结构的语法性和上下文连贯的要求，在空格处填入一个适当的词或使用括号中词语的正确形式填空，并将答案填写在答题卡标号为16—25的相应位置上。 in social life, time plays a very important part．in the u.s.a.,guests tend to feel they are not highly regarded if the invitation 16 a dinner party is extended only three or four days
