粘性土的界限含水量是土体的固有指标，与环境变化无关。
参考答案：对
During our stay in London, the guide book ___ a great help. We all had a wonderful time.
A. behaved B conducted C. served D. proved
列属于定期维护的是（）。
A、季节维护
B、走合维护
C、二级维护
D、技术维护
