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The question asks what value is commonly printed on a fluorescent tube-light. These values represent the correlated color temperature (CCT), specified in units of Kelvin (K), which describes the color of light emitted by the tube.
Option 1: 220 K, is not correct as it signifies a very low color temperature, below even that of a candle`s light, which is around 1500K.
Option 2: 273 K, also is not correct as it is far too low and would represent a color temperature below that of a standard incandescent light bulb, which is around 2700K.
Option 3: 6500 K, is the correct answer. A fluorescent tube-light often has a color temperature of 6500 K, indicating a "daylight" color temperature, which is a bright white light.
Option 4: 9000 K, is wrong because the light at this color temperature would appear slightly blue, and is not generally used for common room lighting but rather specialized purposes, like aquarium lighting.
Therefore, the common value printed on a tube-light corresponds to a "daylight" CCT of 6500 K.