“一分部署，九分落实。”全面深化改革重在落实，要使每—项改革方案都落到实处，重点是抓住领导干部这个关键少数。之所以要“抓住关键少数”，是因为（   ）

①能否抓住主要矛盾对全面深化改革的成败起决定作用

②抓住领导干部这个关键少数就把握了事物的本质和主流

③关键部分的功能及其变化会对整体的功能起决定作用

④全面深化改革任务的确定和落实需要运用综合的思维方式

生物学的研究对象是（    ）

Dear Daming，

    Thanks for your letter and the wonderful photos. I like them very much.

Here are some of my photos. I'm sending them to you . In the first photo，it is snowing. I'm making a snowman with my friends. In the second one，the sun is shining and the wind is blowing. I'm flying a kite in the park. In the third one，I'm swimming in the sea. In the last one，I am with my sister Lucy. We're playing chess.

Best wishes to you and your family.

Love，

Jack

根据书信内容选择正确答案。

一天中气温最高和最低的时间分别是（　　）