20. ______________, but at present this process is prohibitively expensive.
(A)Recovering uranium from seawater may be worthwhile to do someday
(B)The recovery of uranium from seawater someday be worthwhile
(C)To recover uranium out of seawater might have been worthwhile someday
(D)It might someday be worthwhile to recover uranium from seawater
寫作批改
VIP與詳解卡管理
私人筆記( 0 )
