土方的压实工作应先从中间开始，逐渐向边缘推进，这样碾压可以避免边缘土被向外挤压而引起塌落现象。
参考答案：错
During the students’ first teacher training year, they often visited schools for the _____ of lessons.
A．examination
B．investigation
C．inspection
D．observation
细菌性痢疾的肠道病变特点为（）。
A.浆液性炎
B.纤维素性炎
C.肉芽肿性炎
D.出血坏死性炎
E.蜂窝织炎
