Final answer:
Cancer staging determines if the cancer is invasive, the tumor size, and if the cancer has spread to distant sites.
Step-by-step explanation:
Cancer staging is the process of classifying cancer based on factors such as tumor size and the extent to which the cancer has spread. It helps determine if the cancer is invasive and if it has spread to distant sites. The correct answer is D. 1, 2, and 3 as cancer staging involves assessing all three of these factors.