the best times to visit shangri-la in spring and autumn because the temperature is __ its mildest.为什么这里填AT呢?可以翻译一下么?

The Best Of Times 歌词 You go through the worst times in life to get to the best. in the best of times to do what you want to A fire drill is,to put it mildly,an inconvenient exercise at the best of times. the best of times英语作文 美丽时光 THE BEST OF TIMES怎么样 vi to It was the best of times and the worst of These are the best times of the year .中文意思 The best wish to all the best to the best way to It is the best of times.It is the worst of times We shared the best of times 3Q her 1998 book about the death of her son was shot to the top of the New York Times best-selling listas soon as it came 英语翻译：I did my best to prepare for it and I have gone through the notes so many times ,but I still couldn't figure out the answer . the best times to visit shangri-la in spring and autumn because the temperature is __ its mildest.为什么这里填AT呢?可以翻译一下么? Try to be the best