单选题
It is virtually impossible to______the number of people in the world who have acquired an adequate working knowledge of English in addition to their own languages.
【正确答案】
D
【答案解析】estimate意思是form a judgment或calculate“估计”；assess“估价”；appraise“评价”； evaluate“决定……的价值”。句意为：“实际上不可能估计出世界上有多少人除了自己的母语以外熟练地掌握了英语并用它做工作语言。”