Step 1: Understanding the Concept:
A survey that covers every unit of the population is called a census.
Step 2: Analyzing the Options:
• (A) Sample survey: Covers only a subset of the population.
• (B) Pilot survey: A small-scale trial survey.
• (C) Census: Covers every unit of the population.
• (D) Cross-sectional survey: A survey at a single point in time, can be sample or census.
Step 3: Final Answer:
Therefore, option (C) is correct.