溶解氧在水体自净过程中是个重要参数，它可反映水体中（）。
A、耗氧指标
B、溶氧指标
C、耗氧与溶氧的平衡关系
D、有机物含量
参考答案：C
目前认为鼻咽癌的发生与________、________．________、________等因素有关。
His sacrifices for the country were never officially ________________, which made all of us feel
discouraged. [ ]
A. acknowledged
B. appealed
C. recommended
D. evaluated
