来自胡兆炜的问题
Scientistsfoundmanystones---withnumberonthemountains.A.markingB.markedC.beingmarkedD.havebeenmarked选B,why?
Scientistsfoundmanystones---withnumberonthemountains.A.markingB.markedC.beingmarked
D.havebeenmarked选B,why?

