1)选答案D.原因是:前后两个分句中间有关联词but,两个分句都要有自己的主语.而第一个分句有主语的只有答案D,所以选D.
注意它与这道题的区别.______several times,he still doesn't know how to do it properly.如果是这样的话,答案就要选C了.
2)选答案A.原因是:blamed在这里是做定语的,还原成定语从句的话,应该是.Her driver who is blamed for the accident had not been driving carefull.而who is 可以省略,所以就选A．