设正数数列{an}的前n项和为Sn,且存在正数t,得到对于所有的自然数n，有成立，若＜t,则t的取值范围是_________.
16．仿照示例，为学校文学期刊拟一个刊物名并说明理由。 刊物名：《水滴》 理由：“绳锯木断，水滴石穿”，水滴有坚韧执著的力量，水滴有不畏艰
我国现存的第一部完整的农业科学著作是 A.《齐民要术》 B.《兰亭序》 C.《水经注》 D.《九章算术》
在人类文明庄严的通道上，任何一个出口处，中华文明无处不在。在美国最高法院大楼的“司法、自由的护卫者”纪念碑上，刻有三个石像，分别是颁
肉毒碱（化学式为C7H15NO3）是一种具有多种生理功能的物质，被公认为是人体必需的营养物质和最佳的减肥营养素。下列关于肉毒碱的叙述错误的是
Time is a problem for children, states a news report for a new Swiss watch．Children in some countries learn time slowly because they don't wear watches and parents don't really know how to teach the
Don't return the video to Peter, I_ it. A. don’t watch B. won't watch C. haven’t watched D. wasn't watching
To make room for teachers’ correction, the students had better write their composition _____. A. every two line B.
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