已知函数 $f\left(x\right)=\{\begin{array}{l}\hfill \\ \hfill \end{array}\begin{array}{c}\left(a-2\right)x-1,x\le 1\\ {\text{log}}_{a}x,x>1\end{array}$ ，若 $f\left(x\right)$ 在 $\left(-\infty ,+\infty \right)$ 上单调递增，则实数 $a$ 的取值范围为（   ）

某一化石采集队，在甲、乙、丙三个不同的地层内挖掘到许多化石．记录清单如下：甲地层（恐龙蛋，始祖鸟，龟），乙地层（马，象牙，犀牛），丙地层（三叶虫，乌贼，珊瑚）．这些地层依地质年代远近排列应是（　　）

根据短文理解，选择正确答案。The British Museum
What's on
    Although many parts of Asia have long been connected through trade along Silk Road and shared religious systems, there are strong regional differences. In addition to various languages, Asia has developed its cultural networks, patterns of government, technology and styles of artistic representation.
    The diverse cultural life of Africa has been expressed through everyday cooking objects and unique works of art since ancient times. The Museum's collection of over 200,000 African items includes archaeological and contemporary material from across the continent.
    The Iron Age was a time of big change for the people of Britain and Europe.Iron replaced bronze as the material used to make tools and weapons, while religion, art, daily life, economics and politics changed greatly.
Admission and opening times
    The Museum is free and open daily 10:00-17:30 except Friday, and is open until 20:30 on Fridays, except Good Friday. The Museum is open every day except for 24,25 and 26 December and 1 January.
Museum shops
Bookshop
Monday-Thursday 10:00-17:30 Friday 10:00-20:00
Saturday 10:30-17:30 Sunday 10:00-17:30
Collections shop
Monday-Thursday 09:30-17:30 Friday 09:30-20:00
Saturday 09:30-17:30 Sunday 10:00-17:30
Getting here
By Tube
Nearest underground stations:
Tottenham Court Road(500m) Holborn (500m)
Russell Square(800m) Goodge Street(800m)
By bus
Buses that stop near the Museum:1,8,19,X25,38,55,98,242
By car
    The Museum lies within the Congestion(拥堵) Charge Zone. There is little on-street parking nearby. The nearest car park to the Museum is located at Bloomsbury Square. There is limited parking in the Museum's open space for disabled visitors only.

九年级数学兴趣小组经过市场调查，得到某种图书每月的销售与售价的关系为函数关系如下表：

售价（元/本）	50	55	60	65	…
月销量（本）	2000	1800	1600	1400	…

已知该图书的进价为每本30元，设售价为x元．

做托里拆利实验时，下列现象中可确认管中进入了少量空气的是（　　）