When he was running after his brother, the boy lost his ___ and had a bad fall.
A:balance
B:chance
C:memory
D:place
1+tan75°1-tan75°=( )
①创造了巨大的生产力 ② 是生产技术划时代的变革 ③使阶级结构发生了重大变化 ④使人类进入了“电气时代”
阅读诗歌,回答问题。
野步
周密
麦陇风来翠浪斜,草根肥水噪新蛙。
羡他无事双蝴蝶,烂醉东风野草花。