21. What is the main idea of this article?
(A) We should grow crops that won’t need much fresh water.
(B) The lack of fresh water is a problem that keeps getting bigger.
(C) Scientists have invented new ways to save fresh water.
(D) African countries are the hardest hit by shortage of fresh water.
詳解 (共 2 筆)
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水是我們最重要的自然資源。然而，儘管它覆...
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Demand for fresh wat...
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