What could be the cause of spontaneous shutdowns in computers used for CPU-intensive work in a poorly cooled room?

The correct answer is overheating, as it is a common cause of spontaneous shutdowns in computers that are involved in CPU-intensive tasks, especially in environments with insufficient cooling. When a computer's CPU is under heavy load, it generates a significant amount of heat. If the cooling system (fans, heatsinks, etc.) cannot dissipate that heat effectively due to poor ambient conditions, the CPU temperature can reach critical levels. To protect itself from potential damage, the system will initiate an automatic shutdown.

In contrast, while hardware failure, power supply issues, and software crashes can also lead to shutdowns, they are not directly related to the cooling conditions of a room during intensive CPU operations. Hardware failure typically results from long-term stress or age, power supply issues might cause instability irrespective of CPU load, and software crashes usually hint at bugs rather than environmental factors. Given the specific scenario of a poorly cooled room with high CPU usage, overheating is the most likely cause of the shutdowns.