A:焊接
B:榫接
C:铆接
D:钉接
①分别以A,C为圆心,a为半径(a> 12 AC)作弧,两弧分别交于M,N两点;
②过M,N两点作直线MN交AB于点D,交AC于点E;
③将△ADE绕点E顺时针旋转180°,设点D的像为点F.
根据要求写句子。
①雅鲁藏布大峡谷的发明,让人们兴奋不已。(修改病句)
②教室里传出歌声。(扩句)
③指南针是我国古代的四大发明、(修改病句)
— Are there any flowers _______ the tree.— No. But there are many birds _________ it.