Which scientific design has limitations due to oversimplification?
In a study of the interaction of air quality and crop yields, a computer compiles data that are collected by farmers from countries around the world.
In a study of the effectiveness of a new drug on cholesterol, rhesus monkeys receive different strengths of the drug over a period of six weeks.
In a study of the relationships between plants and their pollinators, researchers observe twenty plant plots in a meadow every day for three months.
In a study of the effect of lawn fertilizer on the health of a backyard pond, biologists grow two colonies of duckweed in a large flask to represent pond ecosystems.