问题补充:
It is not enough only the rules of grammar if you want to learn English well.
A. keeping in the mind
B. to keep in mind
C. to keep in your mind
D. keeping in your mind
答案:
A. keeping in the mind
(答案→)B. to keep in mind
C. to keep in your mind
D. keeping in your mind
解析:选B。keep sth. in mind 为固定短语,意为“记住,记在心里。”only to keep sth. In mind为动词不定式作主语。