23. There is evidence that solar energy either is now economically competitive with conventional sources of heat ______ so within a few years.
(A) will be or
(B) but will be
(C) or will be
(D) and will be

答案：登入後查看
統計： A(22), B(16), C(295), D(59), E(0) #209294

詳解 (共 2 筆)

#6025306
either .... or ........
(共 257 字，隱藏中）
前往觀看
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0
#182257
conventional  習慣的,慣例的
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