Intepretation of choice compositor and occurence into xml schema

It is not clear for me how to interpet attribute elements
minOccurs/maxOccurs into <choice> element having sub-elements that also have
minOccurs/maxOccurs attributes as for example 

Schema 1:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified" attributeFormDefault="unqualified">
   <xs:element name="document">
      <xs:complexType>
         <xs:choice minOccurs="0" maxOccurs="2">
            <xs:element name="A" minOccurs="1" maxOccurs="1"/>
            <xs:element name="B" minOccurs="1" maxOccurs="1" />
            <xs:element name="C" minOccurs="1" maxOccurs="1"/>
         </xs:choice>
      </xs:complexType>
   </xs:element>
</xs:schema>

Schema 2:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified" attributeFormDefault="unqualified">
   <xs:element name="document">
      <xs:complexType>
         <xs:choice minOccurs="1" maxOccurs="unbounded">
            <xs:element name="A" minOccurs="0" maxOccurs="1"/>
            <xs:element name="B" minOccurs="0" maxOccurs="1" />
            <xs:element name="C" minOccurs="0" maxOccurs="1"/>
         </xs:choice>
      </xs:complexType>
   </xs:element>
</xs:schema>

Schema 3:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
elementFormDefault="qualified" attributeFormDefault="unqualified">
   <xs:element name="document">
      <xs:complexType>
         <xs:choice minOccurs="1" maxOccurs="unbounded">
            <xs:element name="A" minOccurs="1" maxOccurs="1"/>
            <xs:element name="B" minOccurs="0" maxOccurs="3" />
            <xs:element name="C" minOccurs="0" maxOccurs="1"/>
         </xs:choice>
      </xs:complexType>
   </xs:element>
</xs:schema>


I tried to find more information about this subject on the web, but I didn't
succeed.

Can somebody give me more information about how to interpret schema 1,
schema 2 and schema 3 ?

Thanks for your help.

Yvan