单选题

执行如下更新SQL：update t set b = 5 and a= 2 where a = 1之后，a和b值为?

Question

MySQL中t表存在如下数据

+---+---+

| a | b |

+---+---+

| 1 | 2 |

+---+---+

执行如下更新SQL：update t set b = 5 and a= 2 where a = 1之后，a和b值为： 

A. a = 2， b = 5

B. a = 1， b = 5

C. a =1 ， b = 0

D. a = 1， b = 5