(2019·全國卷Ⅲ)Weseetheskyisblue,

來源：國語幫 2.15W

(2019·全國卷Ⅲ)We see the sky is blue, ________ down in the valley it's darker—it's like on a cloudy day.

but　句意：我們看到天空是藍*的，但在下面的山谷裏，天更黑了，就像*天一樣。前後兩個分句存在轉折關係，故填but。