Of the risk factors listed, the one you can control is associated with your friends smoking. While you can't control your friends' behavior directly, you can choose whom you spend time with and whether you engage in similar behaviors. The other options, such as family history of heart disease or the incidence of high blood pressure in your ethnic group, are inherent risk factors that you cannot change. Unintentional accidents, while a concern, are also not a risk factor you can control directly.
So, the key point is that you can control your own choices and behaviors regarding health, making the influence of your friends' smoking a relevant risk factor you can navigate.