说寡头会造成低效率的资源配置是因为产品价格( )边际成本。
A. 等于
B. 小于
C. 大于
D. 上述情况都存在
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氯化钠注射液属于胶体溶液。()
A. 对
B. 错
胶体分散系的粒子直径范围是( )。
A. 1-100nm
B. <1nm
C. >100nm
D. 1-10nm
This is one of the largest bridges that______on this river.
A. is ever built
B. has ever been built
C. was ever built
D. has ever built