向量$\overrightarrow{a}=(1,2),\overrightarrow{b}=(-2,3)$,若$m\overrightarrow{a}-n\overrightarrow{b}$与$\overrightarrow{a}+2\overrightarrow{b}$共线（其中$m,n\in R,n\ne 0$),则$\frac{m}{n}=（ \; ）$

two chairs.

狄德罗《百科全书》说：“自由是天赐的东西，每一个同类的个体，只要有理性，就享有自由的权利……不是国家属于君主，而是君主属于国家。”此言体现的主张有(  )

①个人自由          ②权利平等       ③联邦共和         ④主权在民

如图，⊙O的半径是3，点P是弦AB延长线上的一点，连接OP，若OP=4，∠APO=30°，则弦AB的长为（　　）

阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。（共10小题；每小题1.5分，满分15分）

    In 1863 the first underground passenger railway in the world opened in London. It ran for just under seven kilometers and allowed people to avoid terrible ____ (crowd) on the roads above as they travelled to and ____ work. It took three years to complete and was built using an interesting method. This included digging up the road, ____(lay) the track and then building a strong roof over____ top. When all those had been done, the road surface was replaced.

    Steam engines ____(use) to pull the carriages and it must have been____(fair) unpleasant for the passsengers, with all the smoke and noise. However, the railway quickly proved to be a great success and within six months, more than 25,000 people were using____every day.

    Later, engineers ____(manage) to construct railways in a system of deep tunnels (隧道）, which became known as the Tube. This development was only possible with the ____(introduce) of electric-powered engines and lifts. The central London Railway was one of the most ____(success) of these new lines, and was opened in 1900. It had white-painted tunnels and bright red carriages, and proved extremely popular with the public.