In a conventional domestic refrigerator, the evaporator/freezer coil is located at the top. While colder air sinks, the bottom storage section (the crisper/vegetable bin) is purposefully shielded and insulated from direct cold air convection to maintain warmer temperatures ($+8^\circ\text{C}$ to $+10^\circ\text{C}$) to prevent freezing injury to sensitive vegetables and fruits, making it the least cold compartment.

Option analysis:

• Top of refrigerator cabinet: Situated immediately below or adjacent to the evaporator, maintaining very cold temperatures ($+1^\circ\text{C}$ to $+3^\circ\text{C}$).
• Middle of refrigerator cabinet: Moderate intermediate temperature zone ($+4^\circ\text{C}$ to $+5^\circ\text{C}$).
• Bottom of refrigerator cabinet: Correct, crisper drawers at the bottom are the least cold zone ($+8^\circ\text{C}$ to $+10^\circ\text{C}$).
• Tray meant for storing milk: Located directly beneath the chiller/freezer, highly cold.