Q. 17 and 18 are Assertion (A) and Reasoning (R) based questions. Mark the correct choice as (a) Both (A) and (R) are true and (R) is the correct explanation for (A). (b) Both (A) and (R) are true and (R) is not the correct explanation for (A). (c) (A) is true but (R) is false. (d) (A) is false but (R) is true. Assertion (A) : In Python, a stack can be implemented using a list. Reasoning (R) : A stack is an ordered linear list of elements that works on the principle of First In First Out (FIFO).

Q. 17 and 18 are Assertion (A) and Reasoning (R) based questions. Mark the correct choice as (a) Both (A) and

Question

Q. Q. 17 and 18 are Assertion (A) and Reasoning (R) based questions. Mark the correct choice as

(a) Both (A) and (R) are true and (R) is the correct explanation for (A).

(b) Both (A) and (R) are true and (R) is not the correct explanation for (A).

(d) (A) is false but (R) is true. Assertion (A) : In Python, a stack can be implemented using a list. Reasoning (R) : A stack is an ordered linear list of elements that works on the principle of First In First Out (FIFO).

CBSECBSE Class XII Board 2023MCQ· 1mImportance★★★★★

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Concept understanding — List Stack Operations

Let’s begin with something you already know: a stack of plates in a cafeteria. You can only take the top plate off, and you can only put a new plate on top. You never pull a plate from the middle or the bottom. That everyday action is the core idea behind a stack in computer science — a list where all additions and removals happen at one end, called the top.

Now, in your NCERT textbook for Informatics Practices or Computer Science (Class 11 or 12), when you study List Stack Operations, you are learning how to treat a Python list as if it were that stack of plates. A normal list lets you add or remove items from anywhere. But a stack is a restricted list: you can only work with the most recently added item. This restriction is not a weakness — it is a deliberate design that makes certain tasks simple and fast.

The two fundamental operations are:

Push – adding an element to the top of the stack.
Pop – removing the top element from the stack.

There is also a third operation, Peek (or Top), which just looks at the top element without removing it. And you will often check if the stack is empty before trying to pop.

Note

In Python, you can implement a stack using a list. The append() method acts as push, and pop() (with no argument) acts as pop. Python’s list already has these built-in, so you don’t need to write any special code — you just use the list in a disciplined way.

Why does this matter? Because stacks are everywhere in real computing. When you press the Back button in a web browser, it pops the previous page off a stack of visited pages. When you undo an action in a word processor, it pops the last change off a stack of edits. Even the way your computer calls one function from another uses a stack behind the scenes. So learning stack operations is not just about lists — it is about understanding a pattern that appears again and again. …

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The assertion is true, but the reasoning is false because a stack follows LIFO, not FIFO.

Let’s take this step by step. The Assertion says that in Python, a stack can be implemented using a list. That is perfectly correct. Python’s built-in list type provides methods like append() to add an element at the end and pop() to remove the last element — exactly the operations needed for a stack. Many textbooks and real-world Python code use lists as stacks, so this part is true. …

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Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2023Set 91/41 markMCQ
$Q. Q. 17 and 18 are Assertion (A) and Reasoning (R) based questions. Mark the correct choice as$
(a) Both (A) and (R) are true and (R) is the correct explanation for (A).
(b) Both (A) and (R) are true and (R) is not the correct explanation for (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true. Assertion (A) : In Python, a stack can be implemented using a list. Reasoning (R) : A stack is an ordered linear list of elements that works on the principle of First In First Out (FIFO).
›Reveal solutionSolution

The assertion is true, but the reasoning is false because a stack follows LIFO, not FIFO.

Let’s take this step by step. The Assertion says that in Python, a stack can be implemented using a list. That is perfectly correct. Python’s built-in list type provides methods like append() to add an element at the end and pop() to remove the last element — exactly the operations needed for a stack. Many textbooks and real-world Python code use lists as stacks, so this part is true. …
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Q.Q. 17 and 18 are Assertion (A) and Reasoning (R) based questions. Mark the correct choice as

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