✅ A. silver iodide and potassium iodide: True Both are used in cloud seeding because their crystalline structures help form ice nuclei, inducing rainfall.

❌ B. silver nitrate and potassium iodide: False Silver nitrate is not used for artificial rainmaking.

❌ C. silver iodide and potassium nitrate: False Potassium nitrate is not used in cloud seeding.

❌ D. silver nitrate and potassium chloride: False Neither chemical is used in artificial rainmaking.

Therefore, option A is correct.