On a hydrocarbon flammability chart the line which extends from 0% to 21.8% oxygen，lying tangent to the flammability range，is called the（）. ["mimimum oxygen content line","critical displacement line","critical dilution line","upper threshold limit"]
不同类型的导管分子次生壁加厚的程度不同，下列哪一种排列正确的表明了壁逐渐增厚的程度？（） ["环纹导管-螺纹导管-网纹导管-梯纹导管-孔纹导管","环纹导管-螺纹导管-梯纹导管-网纹导管-孔纹导管","环纹导管-梯纹导管-螺纹导管-网纹导管-孔纹导管","环纹导管-梯纹导管-网纹导管-螺纹导管-孔纹导管"]
One precaution to take prior to working in a freshly painted compartment where there are an excessive amount of paint fumes, is to （）. ["take shallow breaths of air","ventilate the area","wear a breathing apparatus while working","keep a charged fire hose handy"]
密封胶胶形的质量要求是什么？
以下国家中，癌症的检出率和治愈率最高的是（）。 ["中国","韩国","德国","日本"]
东非大裂谷带是怎样形成的？
