Which statements concerning the relationships between the following classes are true？（）  
class Foo {  int num；  
Baz comp = new Baz（）；  
}  
class Bar {  boolean flag；  
}  
class Baz extends Foo {  
Bar thing = new Bar（）；  
double limit；  
}  

A.The operation col1.retainAll（col2） will not modify the col1 object.
B.The operation col1.removeAll（col2） will not modify the col2 object.
C.The operation col1.addAll（col2） will return a new collection object， containing elements from both col1      and col2.
D.The operation col1.containsAll（Col2） will not modify the col1 object.

A.The code will fail to compile.
B.The constructor in a that takes an int as an argument will never be called as a result of constructing an     object of class b or c.
C.Class c has three constructors.
D.Objects of class b cannot be constructed.
E.At most one of the constructors of each class is called as a result of constructing an object of class c.

A.（a == "Hello"）
B.（a == b）
C.（a == c）
D.a.equals（b）
E.a.equals（d）