Lack of Physical Activity Is a Known Factor Associated with Colon

Lack of physical activity is a known factor associated with colon cancer.However,colon cancer develops even among active individuals.Moreover,several individuals who perform very little levels of physical activity never develop colon cancer.Hence,in the causal relationship between physical inactivity and colon cancer,the lack of physical activity is

A) necessary and sufficient.
B) sufficient but not necessary.
C) necessary but not sufficient.
D) neither necessary not sufficient.
E) confounded.