Free Practice Quiz Question List

5 Polymorphism Online Quiz Questions

Use this free practice quiz with 20 questions to review 5 Polymorphism, test your knowledge, and prepare for your next test or exam.

20 questions

Choose one

1 point

Which statement best describes the central value of polymorphism?

A
It requires every concrete type to use identical internal code.
B
It allows different concrete types to be used through a common abstraction.
C
It means that only subclasses can be instantiated.
D
It replaces all interfaces with concrete classes.

True or false

1 point

A variable is declared as Shape but refers to a Circle object. When a virtual Area() method is called, the declared type determines which override executes.

A
True
B
False

Written response

1 point

What mechanism causes shape.Area() to call Circle.Area() when the variable is declared as Shape but refers to a Circle?

Fill in the blank

1 point

A derived class that can be used wherever its more general type is expected has a relationship with that .

Choose one

1 point

A class DetailedReport overrides BaseReport.Format(), while HiddenReport hides the same method with new. Which statement correctly distinguishes the two designs?

A
The derived method is always ignored.
B
The compiler rejects every call through the base type.
C
A base-class reference can still reach the derived implementation.
D
The new keyword guarantees run-time dispatch.

Choose all

1 point

Which benefits follow from programming against an abstraction such as IPaymentProcessor? Select all that apply.

A
Implementations can change without requiring changes to clients.
B
Tests can provide fake or mock implementations.
C
The caller must know the concrete class used at run time.
D
New implementations can be added without modifying the caller.

True or false

1 point

An interface-based relationship requires all implementing classes to share a common implementation of their operations.

A
True
B
False

Written response

1 point

What design approach lets a Report contain an IFormatter and delegate rendering to it instead of inheriting from separate formatter-specific report classes?

Fill in the blank

1 point

The ability to replace a general type with a more specific type without breaking clients is called . It requires preserving the abstraction's .

Choose one

1 point

Which situation best illustrates duck typing?

A
The object must inherit from a specified base class.
B
The object is accepted if it provides the required behavior.
C
The compiler must generate a separate interface for every object.
D
Only objects with identical fields can be substituted.

Choose all

1 point

Which checks belong to a practical review of whether a subtype is safely substitutable? Select all that apply.

A
It can be passed wherever the supertype is expected.
B
It honors the supertype's preconditions and postconditions.
C
It may impose stronger requirements if its method signatures match.
D
It preserves important invariants of the abstraction.

Open ended

1 point

Explain how programming against abstractions supports changeability and testability. Use the payment-processor example or an equivalent design, and explain why substitutability still matters.

Choose one

1 point

Which guideline correctly distinguishes when inheritance or composition should be used?

A
Inheritance should be used whenever it avoids duplicated helper methods.
B
Composition is appropriate only when no interfaces exist.
C
Inheritance should express a genuine subtype relationship, while composition suits a “has a” relationship.
D
Composition prevents objects from using polymorphic behavior.

Choose one

1 point

Which description best captures the central value of polymorphism?

A
It requires every concrete type to use identical internal code.
B
It allows different concrete types to be used through a common abstraction with specialized behavior.
C
It means a caller must know the exact concrete class before invoking any operation.
D
It replaces all interfaces with static utility methods.

True or false

1 point

In duck typing, code can accept an object because it supports the required operations even when it does not explicitly inherit from a named type.

A
True
B
False

Choose one

1 point

Given Shape shape = new Circle(2);, which implementation is selected when shape.Area() is invoked, assuming Area() is overridden?

A
The call is rejected because Shape has no concrete implementation.
B
The call always executes Shape.Area() because Shape is the declared type.
C
The call executes Circle.Area() because Circle is the run-time type.
D
The call selects an overload based on the constructor expression.

Written response

1 point

What type relationship describes a class that promises to provide the operations specified by an interface?

Choose one

1 point

What is the important behavioral difference between using override and using new for a method in a derived C# class?

A
override preserves dynamic dispatch through a base-class reference, whereas new hides the member.
B
new preserves dynamic dispatch, whereas override makes the method private.
C
override and new always produce identical behavior through a base-class reference.
D
new can be used only with abstract members, whereas override can be used only with nonvirtual members.

Choose one

1 point

A function accepts values through a base abstraction. Which condition is necessary for a new subtype to be safely substitutable?

A
A subtype must expose more public methods than its supertype.
B
A subtype may reject inputs that the supertype accepts if its implementation is more specialized.
C
A subtype is substitutable whenever it inherits the same method names.
D
A subtype must preserve the supertype's behavioral expectations when used through the abstraction.

Written response

1 point

What design approach lets an object delegate work to contained objects that implement an abstraction?