反义词。
神奇____ 脆弱____ 阻碍____
八达岭长城脚下,蜿蜒着一条铁路,它是中国人自行设计和施工的第一条铁路干线,这条铁路是( )
— Would you like to go for a picnic with me?
— ______ I have to help Kate with her Chinese
某物质在氧气中完全燃烧,只有二氧化碳生成,则该物质( )