Concept:Process skills like observation, hypothesis formation, and classification are developed when students design experiments to test material properties.
Explanation:Students first observe each material carefully to see if it conducts electricity.
They then formulate hypotheses about which materials will be good or poor conductors.
Finally, they classify materials (e.g., nails as conductors, paper as insulators) based on their observations.
Measurement and operational definition are not the main skills here because the activity does not involve quantifying or defining terms operationally.
Answer:The correct combination is A, D, B. Option D.