英语高考28.Althoughthecausesofcancer____,wedonotyethaveanypracticalwaytopreventit.
28.Althoughthecausesofcancer____,wedonotyethaveanypracticalwaytopreventit.
A.arebeinguncoveredB.havebeenuncovering
C.areuncoveringD.haveuncovered
如果选项E是havebeenuncovered,那是选E还是A?,还是EA都行?
如何知道语义是正在被发现还是已经被发现?
要详解.