Final answer:
The temperature in compartment B will remain unchanged because the compartments are insulated and no energy transfer occurs between them.
Step-by-step explanation:
When the temperature of the water in compartment A decreases by 10°C, the temperature of the water in compartment B will remain unchanged. The two compartments are separated by a metal dividing wall within a closed energy system, and they are insulated by styrofoam, which means heat transfer between the compartments is prevented. Assuming an ideal scenario where there is no heat loss or gain from outside the system and the insulation is perfect, no energy transfer would occur between compartment A and B; thus, the temperature in compartment B would not be affected by the change in compartment A.