未知题型 The position of the adverb ‘successfully’ in following statement agrees with the conventions of academic writing: The study used an artificial elephant tusk containing a GPS system (全球定位系统) to track the smuggled ivory and to place the tusk into the black market successfully.

单项选择题 CRTS II 型板式无砟轨道CA砂浆调整层设计厚度为（） A. 50mm B. 100mm C. 30mm D. 10mm E. 200mm

单项选择题 The Tay-Sachs patients’ brain cells accumulate a lot of .