第2题: [单项选择]The unit of duration of a dash in Morse Code is(). A. one and one-half times the length of a dot B. twice the length of a dot C. three times the length of a dot D. four times the length of a dot 参考答案:C
第3题: [多项选择]本质安全具体包括的内容是( )。 A. 预防 B. 措施 C. 失误 D. 方针 E. 故障 参考答案:C,E
第5题: [单项选择]{{I}}Questions 18 -21 are based on the following conversation.{{/I}}How many dollars does the woman have to pay for the metal shelf A. $12.50. B. $15.50. C. $3. D. $15. 参考答案:B 答案解析:[精解] 销售员说以前的价格是12.50,现在涨了3美元。