A:19
B:15
C:14
D:18
抗美援朝战争中用自己的血肉之躯堵住敌人枪口的英雄人物是( )
读“某地气温曲线图”,判断下列说法正确的是( )
- I really want to join the square dance. Can I learn the dance well?
- Yes, Mom! Nothing is impossible ______ you put your heart into it!
一束光线与界面成30°角从A物质射到B物质,反射光线恰好与折射光线垂直,则入射角为 ____,折射角为 ____