It's said that the moon is at its brightest and roundest on that day.可否分析一下,尤其是 at its.

It's said that the moon is at its brightest and roundest on that day.
可否分析一下,尤其是 at its.

是为了强调那一天
就单单看the moon is at its brightest blah blah. at这个介词是连结is和its的桥梁,没有这个词句子就不通了
这个道理就跟中文当中的“我在我的如花似玉的巅峰状态时嫁给了那个丑八怪”中的“在”一样,语法这个东西又烦又没意思,英语这个东西要靠感觉来的.