按照我国《企业伤亡事故分类））（GB 6441-1986）标准规定，职业伤害事故分为（）类。
A．18
B．19
C．20
D．21
参考答案：C
To everyone’s surprise , Alex _____ play chess very much when he was only four .
A．might
B．should
C．can
D．could
