你好，这一题我有做过，是四级考试语法题目吧？题目完整的是The scientists became very excited as they felt they were______of a discovery.答案是D。根据题意，并不是说科学家们站在真正意义上的边境，而是对于一个新发现即将要实现的边缘。推荐答案的四个翻译都准确，所以根据意思知道选D，不懂可以再追问 :)...
The scientists became very excited as they felt they were ( C)
A.on the crest在波峰
B.on the surface在表面上
C.on the borderline冲出边境，就在边界
D.on the brink即将；边缘上...
