为什么you should understand the traffic rule by now you have had it
问题描述：
为什么you should understand the traffic rule by now you have had it
expiainde often enough 中要用expiainde而不能用to explain
答
从整个句子分析来看,后面的you have had it explained often enough句中存在这样的句型：have had it explained.忽略掉过去完成时have done结构,我们有have it explained,即have sth done结构,表示某事已经被完成.如...