Which of the following types of animal virus requires RNA-dependent RNA transcriptase to be replicated? A) +SSRNA viruses B) SSDNA viruses C)-SSRNA viruses D) retroviruses E) dsDNA viruses Question 48 Which of the following statements concerning B cell receptors (BCRS) is FALSE? A) They are formed in response to an encounter with an antigen. B) They are complementary in shape to a specific antigenic determinant that they may or may not encounter. C) They are bound to the surface of B lymphocytes and have two antigen-binding sites. D) Each B lymphocyte is randomly generated with antibody variable regions that determine its BCR. E) Scientists estimate that each person forms at least 1011 different types of B lymphocytes with distinct BCRS. O C O D O E Question 49 How is the development of autoimmunity normally prevented? A) Tlymphocytes that respond to autoantigens in the thymus undergo clonal deletion. B) T lymphocytes require a specific set of cytokine signals to become activated. C) Regulatory T cells suppress autoimmune responses. D) Clonal deletion of T cells and regulatory T cell suppression prevent autoreactive T cell activation. E) Clonal deletion of T cells, lack of necessary cytokine signals, and regulatory T cell O B O D o E