第21题: [单项选择]The National Safety Council urges drivers and passengers to wear seat belts as a warning against injury. A. caution B. precaution C. security D. safety 参考答案:B 答案解析:[解析] 为了预防伤害,国家安全部要求司机和乘客系好安全带。caution小心,警惕。如:He told us to proceed with caution.他要我们谨慎行事。precaution预