Mark the letter A; B; C; or D on your answer sheet to indicate the most suitable response to complete the following exchange, Mark the letter A; B; C or D on your answer sheet to indicate the most suitable response to complete the following exchange, Mark the letter A. B. C or D on your answer sheet to indicate the most suitable response to complete the following exchange., Mark the letter A. B. C. or D on your answer sheet to indicate the most suitable response to complete the following exchange.