张节理产状（），延伸（），节理面（），节理在尖灭处呈（）状。
参考答案：不稳定，不远，粗糙不平，分叉状或树枝状
“人固有一死，或重于泰山，或轻于鸿毛。”这句话出自[ ]
A．汉文帝
B．汉武帝
C．司马迁
D．王充
They ____ on this project for l 4 hours, but it’s so difficult to persuade them to have a rest. [ ]
A. had worked
B. have been working
C. worked
D. are working
