Question

class Circle { private double radius; public Circle(double radius) { radius = radius; } }

Answer 1

The correct option is the second option i.e.

The program will compile, but you cannot create an Object of Circle with a specified radius. The object will always have radius 0.

The reason being is not using this keywork when assigning user passed radius.
Due to not using this keywork radius in Circle constructor is being treated as a local variable and it shadows the global radius variable.

To avoid the above issue i.e. radius always being 0, the correct way to write is:
1) public Circle(radius) { this.radius = radius; )

                       OR

2) public Circle(someOtherVariableName) { radius = someOtherVariableName; }