Mary worked harder at English than__ in her class.

A.the other students. 因为句子后面有规定范围是in her class,所以选A。如果后面没有范围的话就选B。

选A the other这里是做形容词修饰后面的students.

类似： i'm taller than the other students in my class.

the other students 好一点,the other student in her class 是比其他在她班里的人都好 anyone eles in her class 是任何人在她的班里.

都可以

B