Blue Sky
noun
This is simply a blue sky (aka a blue sky!).
あおぞら
You'd think that this word would use on'yomi readings to read it, but it doesn't (shake that angry fist at the kanji gods!). Instead, it's double kun'yomi, probably because this word is really like two separate words put together, "blue" and "sky." In the previous level you unlocked these two separate words, learning their readings. That means you should be able to read this as well.
One quick note is the rendaku-fication of 空 as well. It becomes ぞら.
青空のせいで海は青いの？
Is the ocean blue because of the blue sky?
未来の子どもたちに、今と同じくらいうつくしい青空をのこしてあげましょうよ。
Let our future generations have the same beautiful sky as we do.
今日は一日中晴れて、青空が広がっていました。
Today, it was sunny all day and the blue sky was above us.