18. Which of the following processes is endothermic?
(A) O₂(g) + 2H₂(g) → 2H₂O(g)
(B) H₂O(g) → H₂O(l)
(C) 3O₂(g) + 2CH₃OH(g) → 2CO₂(g) + 2H₂O(g)
(D) H₂O(s) → H₂O(l)

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