Is that the reason ______ at the meeting for his carelessness in his work? Actually we think he is a man who

is hard ______ himself especially in work. [ ]

A. that he explained to all; on

B. what he explained all; with

C. why he explained to all; at

D. which he explained to all; to

阅读梁实秋《谈时间》片段，回答下列小题：
所以有人宁可遁迹山林，享受那清风明月，“侣鱼虾而友麋鹿”，过那高蹈隐逸的生活。诗人济慈宁愿长时间地守着一株花，看那花苞徐徐展瓣，以为那是人间至乐。嵇康在大树底下扬槌打铁，“浊酒一杯，弹琴一曲”；刘伶“止则操卮执觚，动则挈植提壶”，一生中无思无虑其乐陶陶。这又是一种颇不寻常的方式。最彻底的超然的例子是《传灯录》所记载的：“南泉和尚问陆亘日：‘大夫十二时中作么生’陆云：‘寸丝不挂!’”寸丝不挂即是了无挂碍之谓，“原来无一物，何处染尘埃”这境界高超极了，可以说是“以天地为一朝，万期为须臾”，根本不发生什么时间问题。

这段引文主要说明什么含意