RNA的形成过程如图所示，下列叙述错误的是（     ）

写出下列词的近义词。

叮咛—____     遮蔽—____

商量—____     编织—____

凶狠—____     忽然—____

1930年劳伦斯制成了世界上第一台回旋加速器，其原理如图所示．这台加速器由两个铜质D形盒D₁、D₂构成，其间留有空隙．下列说法正确的是（   ）

阅读和使用地图是学习地理必备的基本技能，运用你所掌握的地图知识，读等高线地形图，图中A、B两点的相对高度是（   ）

     Tom and Mike are good friends. They are good with children. They want to find jobs in summer vacation. This Friday Tom tells Mike that Sunson School Trip needs teachers to help with sports, music and computer. Mike is glad to know that.
    Tom can play basketball, volleyball, and he can swim. Mike can play the violin, the trumpet, the drums and the guitar, and he can swim,too. Tom and Mike like computers very much. Can they join Sunson School Trip?