下列是我国考古发现的不同时期同一类农具，其中最晚出现的应该是[ ]
A 青铜器
B 石耜
C 骨耜
D 铁耜
答案：D
The beautiful mountain village we spent our holiday last year is located in is now part of Guangxi.
A．which; where
B．where; what
C．that; what
D．when; which
如果打开气动油泵的气源开关，并打开液气开关的旁通阀，气动油泵的启停靠（）控制。
A、液气开关
B、手动
C、压力继电器
