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