【单选题】
You create a class library that contains the class hierarchy defined in the following code segment. （Line numbers are included for reference only.）<br /> <img src="https://nimg.ppkao.com/2018-07/zhoulian/2018072710471055592.jpg?sign=e85258dc360fcc57669809828114f5a1&t=62d1891d" /><br /> You create an instance of the Group class. You populate the fields of the instance. When you attempt to serialize the instance by using the Serialize method of the XmlSerializer class， you receive InvalidOperationException. You also receive the following error message： "There was an error generating the XML document."You need to modify the&
A、A
B、B
C、C
D、D
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