Which statement best describes how cancers are classified?
a. cancers are classified according to the type of tissue they affect.
b. cancers are classified according to the rate at which they grow.
c. cancers are classified by how many organs they affect.
d. cancers are classified by the size of the cells that are involved

It depends what you mean by 'classified'. The usual classification we use in pathology would be closest to answer 'a' – carcinoma, for instance, is defined as affecting epithelial cells; or blastoma arises from precursor cells. Grading of a cancer, on the other hand, uses all of the other answers.  So I would say your answer is probably 'a'.

Ihave never had a problem with someone answering questions.. just keep trying