什么是镁砖？
参考答案：
把镁砂破碎，按某种颗粒配比并加入适当结合剂，经高压成型和高温烧成就是镁砖。
A new club in our school at the beginning of this year and now it has many members.[ ]
A. starts
B. is started
C. has started
D. was started
胰岛素瘤的诊断学特征包括()
A．症状因摄取葡萄糖而改善
B．禁食或活动产生症状
C．常伴有高血压症状
D．空腹血糖在50mg/dl以下
E．类固醇可预防症状发作
