The correct answer isB. Forliquid-immersed transformers, the four-letter cooling code is used to describe both thecooling mediaand themethod of circulationfor the internal and external cooling systems. In this code structure, thefirst letteridentifies theinternal cooling mediumthat is in contact with the windings, while thesecond letteridentifieshow that internal cooling medium circulates. This may be by natural circulation or by forced circulation, depending on the transformer design. Thethird letterthen identifies theexternal cooling medium, and thefourth letterindicates thecirculation method of that external medium.
This coding is important in source inspection because the cooling class affects transformer rating, heat dissipation capability, accessories, and verification of nameplate data. During inspection and surveillance, the source inspector checks that the specified cooling class on the nameplate, drawings, and test documentation matches the purchase requirements and transformer design. Misidentifying the cooling code can lead to misunderstanding of the transformer's thermal performance and service suitability. Therefore, thesecond letterspecifically represents thecirculation mechanism for the internal cooling medium.

The correct answer isC. In API 541, during thebearing temperature rise test, a motor bearing is considered to have reachedstable temperaturewhen thetemperature rise does not increase by more than 1°C over a period of one hour. This definition is important because the acceptance of the test depends on showing that the bearing temperature has effectively leveled off under the test conditions rather than still trending upward. If temperature continues to rise beyond that limit, the test has not yet reached thermal stability and the result cannot be treated as final.
This criterion is used in factory testing of large motors to confirm acceptable bearing thermal performance, lubrication condition, mechanical fit, and overall operating behavior at the test load and speed. In source inspection, the inspector verifies not only the final measured bearing temperatures, but also that thetest duration, stabilization criterion, instrumentation, and recorded resultscomply with the governing standard and approved procedures. A 30-minute interval is not the API 541 stability definition, and a 2°C rise in one hour is too permissive. Therefore, the correct API 541 requirement isa rise of not more than 1°C in one hour, which makesoption Cthe verified answer.

The correct answer isC. A properlockout/tagout procedurefor electrical work must include a requirement totest for absence of voltagewherever there may be direct exposure to electrical hazards. Lockout and tagout are not complete merely because disconnecting means have been opened and locked. The worker must verify that the circuit or equipment is actually de-energized before contact, because stored energy, incorrect isolation, backfeed, or mislabeled circuits can leave hazardous voltage present.
In electrical safety practice, this verification is a critical step between isolation and the start of work. The procedure therefore needs a clearvoltage-testing requirementusing an appropriate test instrument and safe work method. This aligns with the source inspection and electrical safety mindset reflected in the API guide, where conformance to procedure, verification steps, and documented controls are essential to safe handling of electrical equipment.
Option A is too general because arc flash PPE may be required for certain tasks, but it is not the core procedural verification step in lockout/tagout. Option B is vague, and option D adds current testing, which is not the standard required element. The required inclusion isvoltage testing.