The body does not typically mount an immune response to cancer. Under which circumstances would you predict that the body would mount a defense against cancer?

a. It must produce an abnormal protein that distinguishes it from normal body cells.
b. It must release cellular peptides that the body recognizes to be defended against.
c. It must become large enough to make its own T-cells for the body to respond.
d. it must become involved in the body's blood supply before the body can respond.

In the initial stages of cancer our body is unable to distinguish between cancerous cells and normal body cells and develop immune response against cancerous cells because cancerous cells have the ability to down regulate β2 microglobulin (β2M) which is attached to α chain of MHC 1 (Major histocompatibility complex) through non-covalent interaction. But, in the later stages of cancer, the cancerous cells start to produce unusual proteins so it becomes easier to distinguish them from other normal cells of the body and as a result of it body starts developing defense against cancerous cells.

MHC-1 are expressed on the surface of nearly all nucleated cells and plays a very important role in recognizing any foreign proteins/carbohydrates/lipids which are present either on the surface of pathogens or produced by them so that it could represent them to the cytotoxic T cells so as to kill them.