Which of the following is a major risk factor for venous thrombosis?

The major risk factor for venous thrombosis among the options is e. Cancer.

Cancer significantly increases the risk of venous thrombosis due to factors like hypercoagulability associated with malignancy and treatment-related factors. While smoking, high cholesterol, hypertension, and diabetes mellitus are risk factors for various cardiovascular conditions, cancer is more directly linked to an increased risk of venous thromboembolism.