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举一反三
【单选题】In many places water is becoming scarcer. Treating it as a right makes the scarcity worse. Ideally, efficient water use would be encouraged by charging for it, but attempts to do so have mostly proved...
A.
People should only be entitled to certain amount of water free.
B.
People can borrow water from their neighbors when necessary.
C.
People are free to bargain for water in market in their daily lives.
D.
People have the right to trade water to raise water productivity.
【单选题】犊牛管理：系统上0-2月龄死淘率的计算，以下说法正确的是
A.
取查询条件月份里，总的死亡犊牛数/总的出生牛头数
B.
取查询条件月份里，死亡犊牛月龄在0-2月龄之间的牛头数/这个月份总的出生牛头数
C.
需要使用离场登记数据和产犊登记数据
D.
取查询条件月份里，死亡犊牛月龄在0-2月龄之间的牛头数/J16向前推2个月份出生的总牛头数