Which of the following is/are true for an abstract class?
1. A class is declared abstract by prefacing the definition with the word abstract.
2. A class is declare abstract by using the keyword implements.
3. It is a class that really isn’t supposed to ever be instantiated but instead serves as a base class.
4. Attempting to instantiate an abstract class results in an error.

interface Base{ boolean m1 (); byte m2(short s);}

1. interface Base2 implements Base {}2. abstract class Class2 extends Base { public boolean m1(){ return true; }}3. abstract class Class2 implements Base {}4. abstract class Class2 implements Base { public boolean m1(){ return (7 > 4); }}5. abstract class Class2 implements Base { protected boolean m1(){ return (5 > 7) }}

A. public class Circle implements Shape { private int radius; }B. public abstract class Circle extends Shape { private int radius; }C. public class Circle extends Shape { private int radius; public void draw(); }D. public abstract class Circle implements Shape { private int radius; public void draw(); }E. public class Circle extends Shape { private int radius; public void draw() { /* code here */ } }F. public abstract class Circle implements Shape { private int radius; public void draw() { /* code here */ } }