It is evidence that solar energy either is now economically competitive with conventional sources of heat or will be so within a few years.
AIt is正確答案
Beconomically competitive
Cor will be
Dso
答案與詳解
為什麼答案是 A
It is evidence 會被理解成它是證據，無法自然表達有證據顯示太陽能具有競爭力。此處應改為 There is evidence that...，或改成 It is evident that...。
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