半坡原始居民生产的陶器主要是[ ]
A．彩陶
B．黑陶
C．白陶
D．黄陶
答案：A
We must keep the classroom _____. [ ]
A. clean
B. to clean
C. cleaning
D. cleaned
钻芯法检测中芯样试件加工完毕后即可进行抗压强度试验。
