With the sole exception of System.Object, which does not inherit from any other object type, all object types must either explicitly or implicitly declare support for (inherit from) exactly one other object type. The graph of the inherits-relation must form a singly rooted tree with System.Object at the base, i.e. all object types must eventually inherit from the type System.Object.
An object type declares it cannot be used as a base type (be inherited from) by declaring that it is a sealed type. It is an error if an object type is marked both abstract and sealed at the same time.
CLS Rule 21: A CLS-compliant class must inherit from a CLS-compliant class. System.Object is CLS-compliant.
Arrays are object types and as such inherit from other object types. Since arrays object types are manufactured by the VES, the inheritance of arrays is fixed. See Array Types.