全为齐齿呼韵母的一组是(    )。
   A．金、永、力、此    B．拥、前、家、师
   C．咬、两、结、月    D．衣、列、流、小

Mounting evidence has led astronomers to just an improbable conclusion; At least 90 percent and possibly 99 percent of all matter in the universe is completely【C1】______ . Astronomers call this stuff dark matter. An astronomer first reported the matter after noting some unusual behaviour in visible matter. In 1993, Swiss astrophysicist Fritz Zwicky concluded that 【C2】______ was causing strange gravitational effects【C3】______ these galaxies. Galaxies are like【C4】______ islands in deep space【C5】______ billions of stars that are held together by the force of【C7】______ .Some galaxies are part of【C6】______ systems called clusters; which contain many galaxies. Most galaxies; belong to smaller systems called groups. Groups and clusters in 【C8】______ form. even larger【C9】______ known as super-clusters. Just【C10】______ the force of gravity keeps stars together in galaxies the force of gravity【C11】______to keep galaxies together in clusters~ This same force of gravity keeps planets【C12】______ around the sun【C13】______ flying off into space. How great a force gravity exerts depends on the mass of the objects【C14】______ and the distance between them, a【C15】______ discovered by Newton. The amount of mass and the distance between objects also【C16】______ how fast the objects travel as they orbit each other. The force of its gravity keeps Earth and the other planets【C17】______ orbit around it. The orbital speeds of the planets【C18】______ with increasing distance from the sun. The planet nearest to the sun travels at an orbital speed of 48 kilometers per second【C19】______ the distant planet Pluto orbits【C20】______ speed of 7 kilometers per second【C1】A．visibleB．invisibleC．perceivedD．tangible 点击查看答案

下面是有关扫描仪的叙述： Ⅰ．光学分辨率是扫描仪的一个重要性能指标 Ⅱ．所有扫描仪都能扫描照相底片等透明图件 Ⅲ．扫描仪的工作过程主要基于光电转换原理 Ⅳ．滚筒式扫描仪价格便宜、体积小，适合于家庭使用 其中正确的是______。A．Ⅰ、Ⅱ和ⅢB．Ⅰ和ⅢC．Ⅱ和ⅢD．Ⅱ和Ⅳ 点击查看答案