But personally I believe a business letter should end with Very truly yours, not Sincerely.
还行,乔治。但是我个人相信一封商业信函应该以“敬上”结尾,而不是“谨启”。
the necessary method of study is to group the relevant material and to take note of all possible variant forms and conditions.
应采取的研究方法是,把有关各方面的材料汇集起来,同时注意任何可能出现的异常情况和条件。