关于惯性，下列说法正确的是 （   ）

阅读下面材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。

    As is known to us, the year 2016 has one extra day in it — February 29th. This is because it's ____ we call “a leap year”. Every four years, the year has 366 days in ____  instead of 365.

    It is called a leap year because hundreds of years ago in England, the extra day wasn't____ (legal) recognized. There is a well-known tradition in the UK____ (associate) with February 29th, introduced many centuries ago. Women are allowed to break with tradition and propose(求婚) to their boyfriends on this day. This all started back in the____ (five) century, when a famous Irish saint made a____ (complain) that women had to wait too long for men to propose. According to the legend, Saint Patrick said any female dreaming of a proposal could ask her boyfriend to marry her on this additional day in February. This so-called tradition____ (write) in law in the thirteenth century. Scotland passed a law allowing women to propose to men in a leap year. It was said that if the men refused, they had to pay a fine!

    Now in 2016, there are calls____ February 29th to become a public holiday. Some people believe that it should be an____ (office) day off, because no one gets____ (many) payments for working an extra day in a leap year. For the moment though, the British still have to go to work on this day.

①降低恩格尔系数，提高捎费水平

②优化产品产业结构，替力推进农业提质增效

③推行绿色生产方式，增强农业可持续发展能力

④培育新的消费热点，加快消费结构升级

  ____ ____ ____

如图是关于双链DNA分子结构叙述正确的是（　　）