Mr Lopez Has a Family History of Cardiovascular Disease and Elevated

Mr. Lopez has a family history of cardiovascular disease and elevated homocysteine levels. A researcher asks Mr. Lopez if he is interested in participating in a trial to look at the effects of a vitamin B₁₂ supplement on cardiovascular events. Why would a researcher hypothesize that a vitamin B₁₂ supplement will reduce Mr Lopez's cardiovascular risk?

A) Vitamin B₁₂ will decrease his HDL cholesterol.
B) Vitamin B₁₂ is required for the metabolism of methionine.
C) Vitamin B₁₂ will constrict the blood vessels.
D) Vitamin B₁₂ is an electrolyte that regulates heartbeat.