无定形硅为黑色粉末,可用镁与SiO2反应制得,其化学反应方程式为: SiO2 + 发布时间:2017-07-06 23:42 │ 来源:www.tikuol.com 题型:选择题 问题: 无定形硅为黑色粉末,可用镁与SiO2反应制得,其化学反应方程式为: SiO2 + 2Mg === Si + 2X 。则X的化学式为[ ]A.Mg B.O2 C.MgO2D.MgO
题型:选择题 用所给词的适当形式填空。1. When she couldn't find her mother, she ______ (begin) to cry.2. —When did the movie ______(begin)? —It _____ (begin) about ten minutes ago.3. At the ______ (begin) of this term, we have two new ______ (woman) teachers.4. How many _______ (wheel) does a bike have ?5. He always _____ (use) this pen to write. 查看答案
题型:选择题 支气管扩张特点是()A.长期咳嗽,咳大量脓痰,反复出现大咯血B.45岁以上伴大量长期吸烟史,持续痰中带血C.咳嗽剧烈时,痰中带血D.低热、盗汗、咳鲜血痰E.夜间阵发性呼吸困难伴咳粉红泡沫样痰 查看答案