Which of the following are true when writing a letter of apology? A: do not condemn（谴责） yourself too severely , as it may reinforce（加强） irratation of the reader B: too much reinforcement of the error would work against the purpose of apology C: an unsolicited (自发的) letter of apology removes a barrier or even preserves（维持） a business relationship D: the more you condemn yourself, the better