In Classroom, you can give a numeric grade, leave comment-only feedback, or do both. You can also return assignments without grades. You can grade and return work from:

The Student work page (A) provides a comprehensive view of all student submissions for a particular assignment. From this page, you can efficiently grade, add private comments, and return work to individual students or the entire class. The Classroom grading tool (D), which is accessed when you click on a student's submission, allows for detailed grading, commenting, and returning of work for that specific student. Both options are correct because they are integrated parts of the grading workflow in Google Classroom. The People page (B) is used for managing students and co-teachers, not for grading assignments. The Stream page (C) is for announcements and general communication, not for the grading process.