why was darcy's proposal rejected by elizabeth? what explaination did he offer for his earlier action

Elizabeth's lively, straightforward, daring character and her disregard for considerations of rank show through clearly in her reaction to Darcy's proposal. Her pride is also evident, for the lack of civility in her refusal is due primarily to injured pride resulting from Darcy's frank explanation of his reservations about proposing to her because of her inferior connections. Darcy admits that the impropriety of the Bennet family made him hope that the two would not marry, but that his main reason for preventing Bingley from proposing to Jane was that he did not think that Jane had any particular regard for Bingley. The only part of his conduct which he is uneasy about is that he concealed from Bingley his knowledge that Jane has been in London for the past few months.