Not knowing what style of iPad to choose  _

问题补充：

NotknowingwhatstyleofiPadtochoose,_______.A.some advice was given to LimingB.Liming had to consult his IT teacherC.so Liming had to consult his IT teacherD.Liming’s IT teacher gave him some advice

答案：

B解析本题考查非谓语动词的用法。有前面的现在分词knowing可知， 所选句子的主语应是其执行者，故只有BD合适。再结合句意可排除D.