【题目】If you want to learn more about this concept, you may _____ Professor Li’s paper.
A.look up to
B.add to
C.look forward to
D.refer to
在线课程【答案】D
【解析】
考查动词短语。句意：如果你想进一步了解这个概念，你可以参考李教授的论文。A. look up to尊敬；B. add to加入；C. look forward to期待；D. refer to涉及；参考。结合句意故选D。