Step 1: Understanding the Question:
The question tests a core concept from the Nature/Principles of Management syllabus.
Step 2: Identifying the correct option:
Labelling — providing identification, descriptive, and informational tags on a product's packaging — is a part of the Product element of the marketing mix, making it fundamentally a marketing activity.
Step 3: Why (A) Finance is incorrect:
Labelling has no direct connection with financial decisions such as raising or investing funds.
Step 3: Why (C) Staffing is incorrect:
Labelling is unrelated to acquiring or managing human resources.
Step 3: Why (D) Planning is incorrect:
While planning underlies every function generally, labelling as a specific activity sits squarely under marketing, not planning.
Final Answer:
Marketing