A:①②
B:②③
C:③④
D:①③
从方框中选择适当的单词完成短文。
What's this on the table? It is a ____ of my new classroom. ____ at the picture. ____ can you see ____ the classroom? I can see a ____ desk in the front of the classroom. Some books are ____ the desk. I can see two white ____ , too. There are____ colored chalks (彩色粉笔n them. ____ is the broom (扫帚)? It’s ____ the door. I like this new classroom.
48×25
=(40+8)×25
=40×25+8×25
=1200
证明溴乙烷中溴原子的存在,下列正确的操作步骤为( )
①加入AgNO3溶液 ②加入NaOH水溶液 ③加热
④加入蒸馏水 ⑤加稀硝酸至溶液呈酸性 ⑥加入NaOH醇溶液.