Which equality comparison of Nullable<_T_> types is false

The C# nullable types - Nullable<T> - override Object.Equals(object) method, as well as overload equality operator (==). The Object.Equals() is a virtual method that accepts any reference type argument. On the other hand, a call to overloaded equality operator (==) goes through strict type checking of arguments at compile time. Therefore, the equality operator (==) overloaded by Nullable< T > can only be applied on operands of type Nullable< T > or T.

This code defines some nullable types, and boxes them to create reference type objects:

// A nullable-int
int? ni = 10;       
// box ni
object oi = ni; 

// box int 10
object oten = 10;

// A null-nullable-int  
int? nni = null;
// box nni  
object onni = nni;

Which one of following equality checks on above data instances would return false?