The best answer is B. Replacing the fans. The key clue is the sequence: normal operation, gradual slowdown, and then sudden shutdown. That pattern is typical of overheating. As temperature rises, modern CPUs and GPUs may throttle performance to reduce heat; if cooling remains inadequate, the system may lock up or shut down to prevent damage. The Quentin Docter study guide specifically states that overheating components may cause intermittent shutdowns and that a PC working for a few minutes and then locking up is probably experiencing a heat sink or fan problem. It recommends checking all fans and heat sinks first. The study guide also notes that motherboards often include CPU heat and fan sensors that can shut the computer down before damage occurs if active cooling fails. Upgrading RAM or adding drive space could improve some performance issues, but they would not usually cause a heat-related shutdown. A failing power supply can cause shutdowns, but the gradual slowdown before power-off makes fan/cooling failure the better match.
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