Final answer:
The T5 tube light (28 watt) is more energy efficient compared to the 40 Watt tube light and the 100 watt bulb, but CFLs and LEDs are even more efficient options.
Step-by-step explanation:
When comparing the energy efficiency of different lighting options, we need to consider their power consumption and the amount of light they provide. A 40 Watt tube light and a 100 watt bulb are both less efficient compared to modern lighting technologies. A T5 tube light that consumes 28 watts is more efficient than the two options mentioned previously. However, compact fluorescent lights (CFLs) and light-emitting diodes (LEDs) are known for their high efficiency and energy saving capabilities. CFLs use about 1/4 to 1/10 the input power of an incandescent bulb with the same light output. Fluorescent lights, both long tubes and CFLs, are about four times more efficient than incandescent lights. Moreover, LED lights can be even more efficient, being twice that of CFLs and last significantly longer, though they may come at a higher cost.
Considering the provided options, the T5 tube light (28 watt) would likely be the most energy efficient. However, when available, opting for CFL or LED lighting would further increase energy efficiency and decrease environmental impact.