The question asks which compounds exhibit reduced solubility as temperature rises. Generally, most solid salts become more soluble in water as the temperature increases. However, some exceptions exist.
- Ammonia (NH3): As a gas dissolved in water, ammonia's solubility actually decreases with an increase in temperature; thus, it has reduced solubility at higher temperatures.
- Sodium chloride (NaCl): NaCl typically increases in solubility with rising temperatures, meaning it does not exhibit reduced solubility as temperature rises.
- Cerium(III) sulfate (Ce2(SO4)3): This compound also tends to increase in solubility with temperature, not decrease.
Based on this information, the only compound that exhibits reduced solubility as temperature rises is NH3.
Thus, the answer is C. NH3 only.