在函数y=2x图象上的点是（   ）

以前，人们往往认为一切生物的生长都依赖阳光。现在科学家发现，在水深超过4000米的可见光不能到达的海底，在高温、高压、剧毒、缺氧的环境里，仍然存在大量海底热液生物，它们靠海底热液带出的能量进行化合作用合成有机质而生存。这从一个侧面表明(        )

①对真理的追求是永无止境的循环过程     

②真理是理论与实践的具体的历史的统一

③客观事物的复杂性决定了认识的反复性   

④认识只有不断超越历史条件才能成为真理

①褒义的：____  ____

②贬义的：____  ____

函数f(x)=sinx在区间a,b上是增函数，且f(a)=-1,f(b)=1，则$\cos \frac{a+b}{2}=$（  ）

要变换形式。每词限用一次

    Chicago is a famous city in the US. If you have a(n) ____to go to the US, it is a good idea ____Chicago.

    In the US, Chicago is the third ____city. It is home to people from all over the world. People move to Chicago from ____ places to live with their families or friends. They come to this city by train, plane or ship.

    The centre of Chicago is ____The Loop. You can see many tall ____ here, even some of the tallest in the world. As you travel away from The Loop, you will find there are places of different ____ cultures (文化l). But you can't travel east out of The Loop ____of Lake Michigan.

    When you travel south of The Loop, you will find ____ like Chinatown. There, people from 'China celebrate many festivals as people in their home town do. They also celebrate the holidays of the US.

    Remember to take many ____ with you when you go to Chicago. Why? Because Chicago is called the Windy City.