Key points about abstract class.What is abstract class?

1.) We cannot create object of abstract class but can create a reference of abstract class.
2.) An inheritance between abstract to abstract classes is possible. So no need to implement abstract base class method into derived abstract class. We implement later in concrete class. 
3.) Abstract class can never be a sealed or static.
4.) An abstract can have both abstract method as well as no-abstract method.
5.) An abstract member can be declared only inside abstract class.
6.) An abstract member cannot be static or private.
7.) An abstract member cannot be marked as virtual.
8.) Concrete class cannot inherited more than one abstract class.