Why class has only public and internal access modifier

Answer 1

You mean public and private? There is also protected and in C++ you also have the IMHO horrible concept of friend.
What access modifier do you miss?

Answer 2

thanks for answer but I am asking in c#

Answer 3

Is the same for C# (and pretty much any other OO language), except for the 'friend' part. So you have private, public and protected.

By the way: your original question didn't mention a language...