【句子】
People in prehistoric times created paints by grinding materials such as plants and clay into powder and then adding water.
史前的人们制造颜料是将植物和泥土等原料磨成粉末，然后加水。
【解析】
1.pre historic
adj.史前的；陈腐的
Some prehistoric people lived in caves.
有些史前时期的人住在洞穴里。
2.grind（不常见）
1)v.磨；压迫；碾碎；磨得吱吱响；逐渐停顿
