Ben was busy taking a training class, ________ we had to wait for him for half an hour.
A:so
B:if
C:or
D:but
下列叙述中,不正确的是( )
分别写有数字0,-1,-2,1,3的五张卡片,除数字不同外其他均相同,从中任抽一张,那么抽到负数的概率是()