下列关于MS培养基的叙述中，错误的是（　　）

①能促进物质循环

②能够帮助植物传粉

③能够帮助植物传播果实和种子

④在维持生态平衡中起重要作用

⑤能改良土壤、有利于植物更好的生长

阅读理解
   The best thing about going to school is learning how to read. Books are great friends. They can help you to learn about anything you want to know. They can go anywhere with you. You can read about animals, faraway places, people, and anything else.
   Books are written by people called authors(作者). Authors think of things they want to write about. They make a plan for a book and start to write .Some authors write books that give us information(信息)and teach us things. Authors are very important people because they help us learn. Find a good book to read and read every day ,You will enjoy your time with a good book.

如图，已知圆O的直径为6，CD为圆O的直径，且CD⊥AB，∠D=15°．则OE的长为（　　）