Which encoding are character variables (char) stor

Which encoding are character variables (char) stored in C#?

Windows1251
UTF-16
KOI-8
Win1252
UTF-4

C# language specification:
http://msdn.microsoft.com/en- us/library/ms228593.aspx
http://msdn.microsoft.com/en- us/library/x9h8tsay.aspx

The char keyword is used to declare an instance of the System.Char structure that the .NET Framework uses to represent a Unicode character. The value of a Char object is a 16-bit numeric (ordinal) value.

Type: char
Range: U + 0000 to U + FFFF
Size: Unicode 16-bit character