At the meeting they discussed three different to the study of radioactive waste.
A. means
B. methods
C. approaches
D. ways
网友回答
A. means
B. methods
(答案→)C. approaches
D. ways
解析：考查名词的搭配。Means要和介词by连用；method要和介词with连用；approach要和介词to连用；way要和名词of连用；本题横线后面有介词to，说明C正确。The approach to…表示“…的方法”；句意：在会议上他们讨论了对于放射性废物的3种方法。故C正确。