下列各项中哪一项属于分析流行病学()
A.现况调查
B.病例对照研究
C.观察某种药物治疗的疗效
D.基础实验室检查
E.将调查数据建立流行病学数学模型
参考答案:B
—Would you like me to help you?
— . [ ]
A. Never mind
B. Well done
C. Yes, please
D. I'd love to
She finds ____________ difficult to work out the maths problem.[ ]
A. it.
B. that
C. this
D. its