Cytotoxic T cells recognize and kill host cells infected by viruses. They recognize these cells by the foreign antigen displayed on the host cell’s:. A. MHC I molecules
B. MHCII molecules
C. toll like receptors

The correct answer is - A. MHC I molecules

Explanation:

Major histocompatibility complexes (MHCs) are presented to different T cells to identify the antigen on the host or infected cell. There are two MHCs - class I and class II. The class I MHC presents to cytotoxic T cells while MHC II to helper T cells.

A cytotoxic T cell only binds to the infected cell displays the foreign antigen such as viruses on the infected cell surface in order to recognize and kill the cells.