设x1，x2，x3，x4，x5，x6，x7是自然数，且x1<x2<x3<x4<x5<x6<x7，x1+x2=x3，x2+x3=x4，x3+x4=x5，x4+x5=x6，x5+x6=x7，又x1+x2+x3+x4+x5+x6+x7=2010，那么x1+x2+x3的值
233. Many westerners have the habit of reading their plates every day. The underlined part probably means _____ A. looking at their plates
化学中常用图像直观地描述化学反应的进程或结果。下列图像描述正确的是( ) A．图①表示压强对可逆反应2A(g)+2B(g)3C(g)+D(s)的影响，乙的压强大
Quickly!Tom，give me ______pen to mark the page.I see______under the book. A./；it B.a;that C.the;one
下列物质在氧气中燃烧，产生大量白烟的是（ ） A. 木炭 B. 铁丝
完形填空 My name is Bob. I’m a middle school student. My home is about two miles 1 school. I usually leave 2 school at about 6: 30. I usually get to school 3 . It takes me about 20 minutes. But
—So,Nancy,you had no difficulty finding your way here? —_____________. A.Yes,no difficulty B.No,none at all C.Yes,no problem D.Nonsense
作为国家正在实施的“西气东输”工程终点站，上海将逐渐改变以煤、石油为主的能源结构，这对解决城市环境污染意义重大。目前上海大部分城市居
