15. Suppose we have two classes defined as follows:
class ApBase extends Object implements Runnable
class ApDerived extends ApBase implements Observer
Given two variables created as follows:
ApBase aBase = new ApBase() ;
ApDerived aDer = new ApDerived();
Which of the following Java code fragments will
compile and execute without error?
Select 1 correct answer:
A. Object obj = aBase ; Runnable rn = obj ;
B. Object obj = aBase ; Runnable rn = (Runnable) obj ;
C. Object obj = aBase ; Observer ob = (Observer)aBase ;
D. Object obj = aDer ; Observer ob2 = obj ;