牛顿一生发表的论文较少，主要的著作是《（）》和《自然哲学指数学原理》
参考答案：光学
各银行在处理跨国托收业务时通常遵循的规则是( )
A．《UCP500》
B．《2000通则》
C．《托收统一规则》
D．《联合国托收公约》
—Each year,_ _ fishes are killed by the polluted water and many people are made sick by the polluted air.
—We should do something to stop it! [ ]
A. million of
B. millions of
C. two millions
D. two millions of
