can we create an object for abstract class

The whole point of an abstract class is that it is not intended to be instantiated - that you can't create an object of that type. Instead, it is intended to provide a "framework" on which actual instances can be built.

For an example, think about cars: A Car is an abstract type: you never buy "A car" - you buy "A Ford Fiesta" or "A Ferrari 458", but they both derive from the base "Car" class, and they have "Car" properties and methods in common: four wheels, somewhere for the driver to sit, steering, engine, and so on. You can jump into any Car derived object and expect to be able to steer it (at least around a car park).
So the abstract Car class might have:

public abstract Car
   {
   public abstract void StartEngine();

   public override TurnLeft(float degrees)
      {
      Turn(degrees);
      }
   public override TurnRight(float degrees)
      {
      Turn(-degrees);
      }
   }

Which would require you to create a SatrtEngine method, but you can optionally cretae your own TurnLeft and TurnRight methods.

There is a lot to think about with abstract classes, so try having a look at the MSDN documentation first: http://msdn.microsoft.com/en-gb/library/sf985hc5.aspx[^]