一般英语语法书在讲解英语的主动语态与被动语态时大都指出，主动语态表示主语是动作的执行者，被动语态表示主语是动作的承受者。但是下列被动句中的主语是动作的承受者吗？
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She was given a gram of radium. 她被赠予一克镭。
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First, it (= farmland) is building on. 第一, 耕地上在搞建筑。
我认为，在句(1)中 a gram of radium 才是动作的承受者，而在句(2)中，houses 才是动作的承受者。farmland 仅仅是个场所。
一般语法书对于被动语态所下的定义是正确的。你所提出的句子可以看作是被动句的特殊情况。由这里我们可以看到，有三种句子成分可以变为被动句的主语：
A. 直接宾语：
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Someone found this wallet in the street. 有人在街上捡到了这个钱包。This wallet was found in the street. 这个钱包是在街上捡到的。
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They gave the Nobel Prize for Physics to her. 他们把诺贝尔物理奖颁发给了她。The Nobel Prize for Physics was given to her. 诺贝尔物理奖颁发给了她。
B. 间接宾语：
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They gave her the Nobel Prize for Physics. /She was given the Nobel Prize for Physics. 她被授予诺贝尔物理奖。
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He gave his wife a camera. /His wife was given a camera by him. 他送给他妻子一架照相机。
C. 介词宾语(参见 agree on, on ):
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She looked after the girl. /The girl was looked after by her. 她照料这个女孩。
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The doctor is operating on the patient./The patient is being operated on. 患者正在动手术。