If we do have that belief, we do not suppose that the cause might have happened, ______

A．Terry is the first one who issued "Report on Smoking and Health".
B．Many articles had already been written on the effect of smoking on human body 30 years ago.
C．Tobacco companies denied the reports that show smoking causing diseases.
D．The problem that smoking causes diseases hasn’t been settled yet.

A．research nowadays is focusing on cloning a human body
B．research nowadays is focusing on recreating a whole man
C．scientists are using material from plants and animals to create new organs
D．scientists are using material from plants and animals to create new medicines