根据句意用所给单词的适当形式填空。每空一词。
World Environment Day is on the _________________(five) of June.
What a ____________(sun) day! Let’s go hiking.
China became the second _____________(large) movie market in the world, behind the US.
We often ask _____________(us) how we can do more for our country.
What do you think is the greatest ______________(invent) of the twentieth century?