1. a (Data Science is not concerned only with big data; it involves both big and small data.)
2. b (Python's re module handles regular expressions.)
3. b (search() matches a pattern at any position in the string.)
4. d (GET requests do not modify server state.)
5. a (BeautifulSoup is used for parsing HTML/XML.)
6. a (The alias ps corresponds to pandas.)
7. c (After dropping row 1, 2 rows remain; original 3 rows minus 1 dropped.)
8. b (Dropping column index 2 leaves 2 columns; original 3 columns minus 1 dropped.)
9. d (Time Series is ordered data, not unordered.)
10. a (The requests module sends HTTP requests to retrieve web content.)
11. d (IndexError occurs because {2} references a missing third argument.)
12. b (ACID stands for Atomicity, Consistency, Isolation, Durability.)
13. c (MongoDB uses ObjectId for _id if not provided.)
14. d (MongoDB is both document-oriented and NoSQL.)
15. b (A MongoDB document is equivalent to a SQL record/table row.)
16. c (find_one() retrieves documents matching a condition.)
17. c (Hamming distance equals squared Euclidean distance for binary vectors.)
18. d (Normalization to [0,1] standardizes data within a specific range.)
19. d (Random values are not a common method for replacing missing data.)
20. b (Cosine similarity between (1,0) and (0,1) is 0.)