Cancer grading is based on a. metastasis. b. local invasion. c. cell differentiation. d. tumor size.

The correct answer is - option B.

Explanation:

Grading is the method of classifying the cells that are cancerous. The grades are provided to such cells is cell differentiation that means how different the cells from the normal cells and how fast these cells are spreading and growing.

Pathologist grade the cancer cells on there differentiation from the normal cells as grade 1 with well, grade 2, moderately differentiated, grade 3 with poorly and in last not able to detect the differentiation in grade 4.

Thus, the correct answer among options are - Option B.