麻烦帮我解释一下这句英文句子中的两个语法问题是高一第一单元的一句话：I can well remember that there was a time when a deep blue sky,the song of the birds,moonlight and flowers could never have kept me soellbound.1.为什么要用“could”这个情态动词的过去式和一般过去时连用,而不是说成could never keep me呢?2.记得keep的用法是keep sb.doing sth.或是keep加上形容词,这里为什么用的是keep加上动词过去式呢?（麻烦不要用宾语啦、宾语补足语啦之类的解释,最好能通俗点,因为听同学给我解释了一遍,几乎听不懂,初中的时候没太学语法,尤其对补足语之类的很是不理解,

麻烦帮我解释一下这句英文句子中的两个语法问题
是高一第一单元的一句话：I can well remember that there was a time when a deep blue sky,the song of the birds,moonlight and flowers could never have kept me soellbound.1.为什么要用“could”这个情态动词的过去式和一般过去时连用,而不是说成could never keep me呢?2.记得keep的用法是keep sb.doing sth.或是keep加上形容词,这里为什么用的是keep加上动词过去式呢?（麻烦不要用宾语啦、宾语补足语啦之类的解释,最好能通俗点,因为听同学给我解释了一遍,几乎听不懂,初中的时候没太学语法,尤其对补足语之类的很是不理解,