题干
As a matter of fact, getting rid of a bad habit is ____________forming a good one.
A：an effort much as
B：much an effort as
C：as an effort much as
D：as much an effort as
答案(点此获取答案解析）
D
与定点 
的距离和它到定直线 
的距离的比是 
∶ 
，记点 
的轨迹为 
.
