按其发生的生物效应机制和作用加以分类的受体是（）
A.肽类受体
B.激素受体
C.自感受体
D.药物受体
参考答案：C
The coal miners________in the coal mine for 10 hours before we came to their rescue.[ ]
A. had trapped
B. had been trapping
C. had been trapped
D. would have been trapped
下列酸中酸性最强是（ ）
A．H4SiO4
B．H3PO4
C．H2SO4
D．HClO4
