蓝宝石其实三氧化二铝里面加入了什么离子形成的()
A、铜
B、镉
C、银
D、钛或者铁
参考答案:D
选出错误的选项并改正。
( ) 1. He is writeing a letter. ________________
A B C
( ) 2. She is cooking carrots in the stove. ________________
( ) 3. Lynn helps her mother washing the dishes. ________________
( ) 4. Can you drying the dishes? ________________
( ) 5. He don't go to school today. ________________
一束光射到平面镜上,入射角是30°,则反射角是 _________ 度,反射光线与入射光线的夹角是 _________ 度;如果这束光垂直射到平面镜上,这时入射角是 _________ 度.