题干
At the meeting, they discussed three difficult _______ to the study of mathematics.
A：approaches
B：accesses
C：means
D：methods
答案(点此获取答案解析）
A
At the meeting, they discussed three difficult _______ to the study of mathematics.
A：approaches
B：accesses
C：means
D：methods
为
上的可导函数，且
和
恒成立,则有( )