Which statement about grab sampling and composite sampling best describes their use?

• A. Grab sampling collects multiple samples over time to estimate average conditions.
• B. Grab sampling detects long-term trends; composite sampling detects spikes.
• C. Composite sampling is never used in regulatory programs.
• D. The best approach depends on the objective; grabs detect short-term spikes, composites assess average conditions over a period or area.

Answer: (D)