“如果你是一滴水,你是否滋润了一寸土地?如果你是一线阳光,你是否照亮了一分黑暗?如果你是一粒粮食,你是否哺育了有用的生命?如果你是一颗最小的螺丝钉,你是否永远坚守在你生活的岗位上?”雷锋的这段话说明（ ）
①.在平凡的岗位上也能实现人生的价值
②.人生价值的实现离不开平凡工作的积累
③.干好本职工作是实现人生价值的基础
④.人生的价值在于奉献
A：①③④
B：①②④
C：①②③
D：①②③④
请用直线将鸟卵的结构与其相对应功能连接起来。
①卵白 ____ a含细胞核，是将来孵化成雏鸟的重要结构
②卵壳 ____ b保护卵的内部结构
③卵黄 ____ c保证胚胎发育识能进行气体交换
④胎盘 ____ d提供营养物质和水分
⑤系带 ____ e主要的营养物质
⑥气室 ____ f固定作用
下列有关“探究酵母菌的呼吸方式”实验的叙述，错误的是（ ）
根据短文内容，选择正确答案。
I am a student in China now. My name is Kelly Smith. I live with my parents, two sisters and a brother in Beijing. My parents teach English in No. 6 Middle School. I study in the same school. I am happy here, because I like my new school and the classmates. They are very kind to me. They like to play with me because I look different from them. I have blue eyes and long blond hair. They often say I look like a doll. Also I speak English well. so lots of students like to tam with me to improve (提高) their English.
