The correct answer is B) Check the bearing for proper lubrication. When the temperature of a line shaft bearing increases above its normal operating temperature, the first immediate action should be to check the bearing for proper lubrication. Insufficient or improper lubrication is often the primary cause of increased bearing temperature, as it can lead to increased friction and wear. Checking the lubrication level and condition is a quick and simple step that can help identify and address the underlying issue before taking more drastic measures like stopping the unit or replacing the bearing. The other answer choices, while potentially appropriate in certain situations, are not the immediate action that should be taken. Stopping the unit and replacing the bearing (A) or conducting a full inspection (C) may be necessary if the lubrication check indicates a more serious problem, but these should not be the first steps. Checking the water circulation to the lube oil coolers (D) is also important, but this would typically be a subsequent step after addressing the lubrication issue.