人们常常喜欢用一些英语名言来作为自己的座右铭，请根据以下信息，给下面5个人选择合适的座右铭来配对。
| ____ Ann works hard at English. She never wastes time. |
| ____ Bill is always afraid of failing exam . He needs more confidence. |
| ____ David has good study habits. He thinks the beginning is very important. |
| ____ Linda is 70 years old, but she still likes learning something. |
| ____ Tom wants to be a professional basketball player, but he can’t play it very well. |
A. Practice makes perfect.
B. Every minute counts.
C. Failure is the mother of success.
D. A good beginning is half done.
E. It is never too old to learn.
与曲线 
切于点 
，则b的值为