String serialize(WeatherClass w)
{
    __________________________
    MemoryStream ms=new MemoryStream();
    xml.Serialize(ms, w);
    String s=Encoding.UTF8.GetString(ms.ToArray());
    return s;
}
序列化函数serialize缺少的语句是：
A、 XmlSerializer xml = new XmlSerializer(typeof(WeatherClass));
B、XmlSerializer xml = new XmlSerializer(WeatherClass);
C、XmlSerializer xml = XmlSerializer(typeof(WeatherClass));
D、XmlSerializer xml = XmlSerializer(WeatherClass);