确定香豆素类抗凝效果的最好方法是测定A．抗血友病因子 B．接触因子 C．出血时间 D

The Gulf of Mexico (墨西哥湾) is being polluted seriously. That has affected _______ several hundred kinds of

sea animals there. [ ]

A. at least

B. at once

C. at birth

D. at times

传统中国不能像同时期西欧那样致力于对物质世界的穷究，发展出自己的现代科学技术，其主要原因是