下列化学用语表述正确的是 （    ）

A．羟基的电子式：

B．硫原子的原子结构示意图：

C．乙烯分子的实验式：C₂H₄

D．3,3一二甲基一1一戊烯的键线式：

David did not regret saying what he did but felt that he     it differently.

A．could express

B．would express

C．could have expressed

D．must have expressed