—Nothing special. I stayed at home and watched a film called Paddington 2.
A:named
B:phoned
C:made
某学校为了了解三年级、六年级、九年级这三个年级之间的学生视力是否存在显著差异,拟从这三个年级中按人数比例抽取部分学生进行调查,则最合理的抽样方法是( )