This is my school. There are many trees and flowers in it. The teaching building is big and tall. There is a big playground in our school. After 4:30 in the afternoon, many students come to the playground to play football and some students play table tennis in the table tennis room.
There are 1,200 students in 25 classes in our school. The students all like to study. The teachers in our school are very good. They help the students to study and the students like them, too.

为确保信息安全，信息需加密传输，发送方由明文→密文（加密），接收方由密文→明文（解密），已知加密规则为：明文a，b，c，d对应密文a+2b，2b+c，2c+3d，4d，例如，明文1，2，3，4对应密文5，7，18，16．当接收方收到密文14，9，23，28时，则解密得到的明文为　____ 　

下列物质的用途，主要利用物质的化学性质的是