Picture a jeweler at work. Magnifier in hand, he examines a stone, studying the way light dances off it. He’s trying to determine whether it’s a diamond or merely cut glass, of engagement-ring quality ...
Science classrooms with scientific equipment and supplies should not be used for non-science courses or activities unless the science materials can be stored in a secured area. Laboratory activities ...
一些您可能无法访问的结果已被隐去。
显示无法访问的结果