Final answer:
The temperature of the water to the nearest degree is 30°C.
Step-by-step explanation:
The given question asks to determine the temperature of water to the nearest degree based on its solubility in 30, 20, 80, and 100 mL. The solubility of a substance is dependent on temperature. Solubility varies with temperature; some compounds become more soluble as the temperature increases, while others become less soluble.
Based on the given options, the closest temperature to room temperature (usually considered to be around 25°C) is 30°C (option a). Therefore, the answer is option a) 30°C.