锁、眼镜、羽毛，最重的是____，最轻的是____。

①加入Al能放出大量H₂的溶液中：Na⁺、K⁺、NO₃^﹣、Cl^﹣、SO₄^2﹣

②在pH=11的溶液中：Na⁺、AlO₂^﹣、NO₃^﹣、S^2﹣、SO₃^2﹣

③由水电离的c（H⁺）=10^﹣12mol•L^﹣1的溶液中：Cl^﹣、HCO₃^﹣、NO₃^﹣、NH₄⁺、F^﹣

④加入Mg能放出H₂的溶液中：Mg²⁺、NH₄⁺、Cl^﹣、K⁺、SO₄^2﹣．

当x=-1时，代数式|5x+2|和代数式1-3x的值分别为M、N，则M、N之间的关系为（  ）

C

    Pliny the Elder (老普林尼) wrote the first encyclopaedia with the help of his nephew. This work was made up of 37 books and had many subjects such as anthropology(人类学) and painting. Through the following few centuries, encyclopaedias were connected to religion (宗教). The first Christian edition appeared in 560 AD, and the first Muslim volume came to light soon after.

    One of the longest encyclopaedias ever was produced in 1403 when The Yongle Encyclopaedia《永乐大典》appeared in China. It had 11,095 volumes. Most of the original work has been lost .through the centuries, and people can see less than 400 volumes today. The word "encyclopaedia" coming from Greek means "a general knowledge". It has been .in use for at least 500 years.

    In the 20th century, the Encyclopaedia Britannica became the most well known western work of this type. At the same time, topical encyclopaedias became the most popular, covering different topics. At the end of the century, many publishers began to publish them in digital formats such as Compact Discs (CDs) and Digital Versatile Discs (DVDs).