单选题 The manufacturer stipulates that ______ factory workers receive proper safety training before being assigned to the assembly line.

【正确答案】 C

【答案解析】[解析] 词汇：形容词
1．空格后factory workers以复数名词出现，选项中修饰复数名词的只有all。
2．A选项entire和B选项whole做形容词时需要用冠词，表示“全体”的含义时，后面一般接单数名词。