True or false? in host-versus-graft rejection, the recipient recognizes the donor tissue as foreign and rejects the transplant; in a graft versus-host rejection, the donor tissue recognizes the recipient's tissue as foreign and the transplant rejects the recipient, causing destruction of the recipient's tissue and possibly death.

The statements above are true;
In a host-versus-graft rejection the recipient's immune system recognizes the donor's tissue as foreign and rejects the transplant. On the other hand, in a graft-versus-host rejection, the donor tissue recognizes the recipient's tissue as foreign and the transplant rejects the recipient, causing destruction of the recipient's tissue and possibly death. Its important also to note that there are two types of rejection, the acute rejection, where the rejection of transplanted tissue that occurs several weeks after transplant. it is delayed hypersensitivity reaction, and the chronic rejection is a rejection of transplanted tissue that can occur at a late time. Immune complexes form in the arteries supplying the graft, choking off the blood supply and the tissue is rejected. 

The correct answer is b