It's not the only two choices available. C# also introduced var back in version 3 (2008), but it did it as a "contextual keyword" - meaning that it remains a valid identifier in any position where it used to be one, even to this day. Pretty much all new C# keywords since the very first version are of this nature:

https://docs.microsoft.com/en-us/dotnet/csharp/language-refe...