Option 1 suggests that using fly-ash based cement in building construction can help in reducing the carbon footprint. Fly ash is a byproduct of coal combustion, and by incorporating it into cement, it not only reduces waste but also reduces the amount of carbon dioxide emitted during the cement production process. Therefore, option 1 is correct.

Option 2 states that using LED-based electric lamps instead of incandescent lamps can help in reducing the carbon footprint. This is because LED lamps are much more energy-efficient than incandescent lamps, meaning they require less electricity to produce the same amount of light. By using LED lamps, less energy is consumed, leading to a reduction in carbon emissions from power plants. Therefore, option 2 is correct.

Considering both options, it is clear that both using fly-ash based cement in building construction and using LED-based electric lamps can help in reducing the carbon footprint. Therefore, option 3, which states "Both 1 and 2" is the correct answer.

Alert - correct answer should be option 3.