C# Standard XmlSerializer and inheritance

Good day everyone!

I have a problem with standard XmlSerializer from C#. In my project I have the next class hierarchy:

[XmlInclude(typeof(B))]
[XmlInclude(typeof(C))]
abstract class A { }

[XmlType("btag")]
class B : A {
    [XmlText]
    public String Value { get; set; }
}

[XmlType("ctag")]
class C : A {
    [XmlText]
    public String Value { get; set; }
}

[XmlRoot(ElementName="dtag")]
class D {
    [XmlArrayItem(typeof(A))]
    public List<A> Items { get; set; }
}

I need to serialize class D in the next XML document:

<dtag>
    <ctag>val1</ctag>
    <btag>val2</btag>
    <ctag>val3</ctag>
</dtag>

But serializer serialize object of D class in the next XML document:

<dtag>
    <Items>
         <C d3p1:type="ctag">val1</C>
         <B d3p1:type="btag">val2</B>
         <C d3p1:type="ctag">val3</C>
    </Items>
</d>

All class names and other details of implementation was omitted and I can't change this class hierarchy. I can change only attributes and add a few fields in classes above. And now is my question - how I can omit tag Items in output XML and make element names ctag and btag?