Computer Knowledge — MCQ Practice Questions & Answers

Question 1

Which data structure is best suited for implementing a priority queue?

Accepted Answer

Correct answer: C. Heap — A heap (binary heap) efficiently implements priority queues with O(log n) insertion and deletion of minimum/maximum elements.

Answer

A. Stack

Answer

B. Queue

Answer

D. Linked List

Question 2

In SQL, what is the difference between INNER JOIN and LEFT JOIN?

Accepted Answer

Correct answer: B. INNER JOIN returns only matching rows; LEFT JOIN returns all rows from left table — INNER JOIN returns only rows with matches in both tables. LEFT JOIN returns all rows from the left table plus matching rows from the right table.

Answer

A. INNER JOIN returns all rows; LEFT JOIN returns only matching rows

Answer

C. Both are identical in functionality

Answer

D. INNER JOIN is faster than LEFT JOIN always

Question 3

Which cloud service model provides virtualized computing resources over the internet?

Accepted Answer

Correct answer: B. IaaS (Infrastructure as a Service) — IaaS provides infrastructure resources (compute, storage, networking). SaaS provides applications, PaaS provides development platforms.

Answer

A. SaaS (Software as a Service)

Answer

C. PaaS (Platform as a Service)

Answer

D. DaaS (Database as a Service)

Question 4

What is the primary purpose of database indexing?

Accepted Answer

Correct answer: B. Improve query performance — Indexes speed up data retrieval by creating optimized lookup structures, reducing the number of disk accesses needed to find data.

Answer

A. Increase storage space

Answer

C. Reduce security vulnerabilities

Answer

D. Eliminate data redundancy

Question 5

In cybersecurity, what does encryption primarily protect against?

Accepted Answer

Correct answer: C. Unauthorized access to data during transmission — Encryption converts data into unreadable format, protecting it from unauthorized access during transmission and storage.

Answer

A. Physical theft of devices

Answer

B. SQL injection attacks

Answer

D. Database schema changes

Question 6

Which sorting algorithm has the best average-case time complexity?

Accepted Answer

Correct answer: B. Merge Sort - O(n log n) — Merge Sort and Quick Sort have O(n log n) average complexity. Merge Sort guarantees this; Quick Sort can degrade to O(n²) in worst case.

Answer

A. Bubble Sort - O(n²)

Answer

C. Insertion Sort - O(n²)

Answer

D. Selection Sort - O(n²)

Question 7

What is the primary function of a query optimizer in a DBMS?

Accepted Answer

Correct answer: B. Determine the most efficient execution plan for queries — The query optimizer analyzes different execution strategies and selects the one with minimal resource consumption and execution time.

Answer

A. Compile SQL queries into machine code

Answer

C. Encrypt sensitive data in queries

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D. Validate SQL syntax errors

Question 8

In machine learning basics, what is the purpose of training data in AI models?

Accepted Answer

Correct answer: B. To teach the model patterns and make predictions — Training data is used to teach AI models to recognize patterns. Test data evaluates accuracy; validation data prevents overfitting.

Answer

A. To test the final model accuracy

Answer

C. To validate model security

Answer

D. To encrypt sensitive information

Computer Knowledge - MCQ Practice Questions