非铠装电缆用于非电气人员经常活动场所的地坪以上1m范围以及地中引出的地坪下0.3m深电缆区段时，应采用具有机械强度的管或罩加以保护。( )
A. 对
B. 错
区别5，8-二羟基蒽醌与5，6-二羟基蒽醌时选用（）
A. 碱液反应
B. 醋酸镁反应
C. 无色亚甲蓝试验
D. α-萘酚-浓硫酸试验
E. 浓硫酸反应
利用草酸盐溶解度差异而分离的是（）
A. 小檗碱和小檗胺
B. 麻黄碱和伪麻黄碱
C. 苦参碱和氧化苦参碱
D. 莨菪碱和东莨菪碱
E. 吗啡和可待因
Questions 14-16 are based on the following passage. You now have 15 seconds to read the questions 14-16. Why do you think the author wrote this passage
A. To explain why language learning is difficult.
B. To teach people to speak English.
C. To compare language learning with other types of learning.
D. To encourage language learners to use these techniques.
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