英语改错My secret of staying young is simple:keeping your mind a

英语改错
My secret of staying young is simple:keeping your mind awake
and you will stay young all over.Take an interest in world
around you,and learn at least the new thing every day.Dont
think that you are ever enough old to go back to school.
一行一错
第一行答案无错 但是我觉得and连接的句子前面的KEEPING该改成KEEP
那第二行为什么是动词原型开头呢?不是说动词的原型不能位于句首吗?除了祈使句.但这里又不是祈使句.第四行为什么把EVER改成了NEVER,
还有就是AND连接的第一个和第二个句子 有无逗号有区别吗？