This PCAP practice question tests your understanding of object-oriented programming. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
class A:
def method(self):
return 'A'
class B(A):
def method(self):
return 'B'
class C(A):
def method(self):
return 'C'
class D(B, C):
pass
print(D.mro())Refer to the exhibit. Which of the following correctly shows the MRO of class D?
class A:
def method(self):
return 'A'
class B(A):
def method(self):
return 'B'
class C(A):
def method(self):
return 'C'
class D(B, C):
pass
print(D.mro())[D, B, C, A, object]
Correct MRO.
[D, A, B, C, object]
Why wrong: A is not first after D.
[D, B, A, C, object]
Why wrong: Incorrect order after B.
[D, C, B, A, object]
Why wrong: B comes before C due to definition order.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
[D, B, C, A, object]
Option A is correct because Python's Method Resolution Order (MRO) for class D, which inherits from B and C (where B inherits from A and C inherits from A), follows the C3 linearization algorithm. The MRO is computed as D -> B -> C -> A -> object, ensuring that each class appears before its parents and that the order respects the local precedence order of D's bases (B before C).
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
[D, B, C, A, object]
Why this is correct
Correct MRO.
Related concept
Read the scenario before looking for a memorised answer.
[D, A, B, C, object]
Why it's wrong here
A is not first after D.
[D, B, A, C, object]
Why it's wrong here
Incorrect order after B.
[D, C, B, A, object]
Why it's wrong here
B comes before C due to definition order.
Common exam traps
Python Institute often tests the C3 linearization rule that the local precedence order (the order of bases in the class definition) must be preserved, so candidates mistakenly reorder bases based on inheritance depth rather than the explicit left-to-right order in the class statement.
Detailed technical explanation
The C3 linearization algorithm, used by Python since version 2.3, merges the MROs of parent classes while preserving consistency and monotonicity. It ensures that in complex diamond inheritance (e.g., D(B, C) where B and C both inherit from A), the MRO avoids duplicate classes and maintains a predictable order, which is critical for cooperative multiple inheritance and correct super() calls. A real-world scenario is designing mixin classes in frameworks like Django or Flask, where MRO determines which method implementation is invoked.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
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FAQ
Object-Oriented Programming — This question tests Object-Oriented Programming — Read the scenario before looking for a memorised answer..
The correct answer is: [D, B, C, A, object] — Option A is correct because Python's Method Resolution Order (MRO) for class D, which inherits from B and C (where B inherits from A and C inherits from A), follows the C3 linearization algorithm. The MRO is computed as D -> B -> C -> A -> object, ensuring that each class appears before its parents and that the order respects the local precedence order of D's bases (B before C).
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
This PCAP practice question is part of Courseiva's free Python Institute certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCAP exam.
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