试样混合不均匀所引起的误差属（）误差和（）误差。
参考答案：偶然；系统
赌博犯罪中（）属于赌资。
A、用作赌注的款物
B、换取筹码的款物
C、通过赌博赢取的款物
D、赌博人员随身携带的款物
He doesn't ____ have foreigners in his caf?, so he doesn't know how to serve the American family. [ ]
A. quite
B. seldom
C. often
D. always
