长石按其主要化学成分可分为钾长石和钠长石两大类。
参考答案：错
An official _____ by some reporters on food problems in Shanghai yesterday. [ ]
A. is interviewing
B. is interviewed
C. was interviewing
D. was interviewed
浇筑剪力墙混凝土时应分层下料，分层振捣且每层厚度为振捣器作用长度的1.5倍
