Final answer:
The variation in genes Factor V and prothrombin is known to greatly increase the risk of venous thrombosis in women using oral contraceptives.
The corret option is E.
Step-by-step explanation:
Factor V and prothrombin gene mutations, specifically Factor V Leiden mutation and prothrombin gene mutation (commonly known as G20210A mutation), significantly increase the risk of venous thrombosis in women who use oral contraceptives. These mutations lead to a hypercoagulable state, predisposing individuals to blood clot formation.
So, the correct option is E) Factor V and prothrombin.