A key principle in fair grading is to base the grade on a combination of effort and participation. This approach takes into account not only the assessments and performance but also the student's engagement and effort in the learning process. It promotes a more holistic view of student achievement and learning.
The other options may introduce bias or inequity into the grading process. For instance, ensuring all students receive the same grade undermines individual performance, while giving higher grades based solely on class contributions can disadvantage students who may not be as vocal but still demonstrate understanding through assessments. Providing extra credit only to struggling students may not foster a fair opportunity for all students to improve their grades.