下列各句中划线成语的使用，全都正确的一项是（    ）

①造林绿化，既能保持水土增加空气湿度，又能降低雾霾发生率，是一举两得的事。

②到了半夜，小说终于脱稿，于三江踌躇满志地摸着胡子，长长松了口气。

③跨越式发展过程中，难免会泥沙俱下，出现各种各样的问题。

④在座的各位都是本领域的顶尖专家，我们请大家来，就是想听听各位的高见，大家不必客气．就姑妄言之吧。

⑤近年来，在种种灾害面前，各级政府防患未然，及时启动应急预案，力争把人民的生命财产损失降到最低限度。

⑥对那些少不更事的年轻人，我们不仅要多加指导，还要给他们更多的锻炼机会，使他们尽快地成熟起来。

如图所示，A瓶盛有澄清的石灰水，B瓶盛有紫色石蕊试液，C杯有高低不同的燃着的蜡烛．回答下列问题：

先通读下面的短文，掌握其大意，然后从A、B、C、D四个选项中选择可以填入空白处的最佳答案。

    Today is Sunday．It's1and warm．My parents，my2and I are all at home.My parents don't have to go to3,and my sister and I don't have to go school.We are all in the yard(院子).Look!My father is4his bike．Hd often goes to work by bike．The bike5takes him about ten minutes．My mother is watering the flowers．The flowers make our yard very6．We all like the flowers．My sister is playing with a dog．It's7pet dog．The dog is very smart．My mother often takes the dog out8a walk after dinner．What am I doing?I'm drawing．I like drawing very much．I want to join the9club at school．

    It's a nice day and we're10in the yard．How happy we are today!