C :

#include<stdio.h>

int main()
{
  printf("This is a C program.\n");
  return 0;
}

C++ :

#include<iostream>
using namespace std;
int main()
{
  cout<<"This is a C program.";
  return 1;
}

Pascal :

program t;
begin
 writeln('This is a C program.');
end.

Java :

public class Main{
	public static void main(String[] args) {
		System.out.print("This is a C program.");
	}
}

Bash :

echo 'This is a C program.
'

Python :

print("This is a C program.")

C# :

using System;


namespace Worx
{
    class Class1
    {
        static void Main()
        {
            Console.WriteLine("This is a C program.");
       
      //      Console.ReadLine();

        }
       
    }
}