the students in Class One are quieter than --in Class Three.

the students in Class One are quieter than __in Class Three。A onesB those Cthem Dthat翻译：一班的学生（复数）比三班的学生安静。两个班学生比较,前后要匹配,故三班学生也为复数。从四个选项中可知C、D选项意思不对排除,AB中ones没B中的those那些更贴切,故个人认为,选择B。