问题补充：
-- Not knowing what style of iPad to choose, .
A. some advice was given to Liming
B. Liming had to consult his IT teacher
C. so Liming had to consult his IT teacher
D. Liming’s IT teacher gave him some advice
答案：
A. some advice was given to Liming
(答案→)B. Liming had to consult his IT teacher
C. so Liming had to consult his IT teacher
D. Liming’s IT teacher gave him some advice
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.
