1. Copper slag is a by-product generated during the extraction and refining of copper. It can be used as a partial replacement for sand in concrete production, thus reducing the demand for natural resources. This reduces the environmental impact associated with sand mining. 2. Cold mix asphalt technology involves producing asphalt mixtures at lower temperatures compared to traditional hot mix asphalt. This results in reduced energy consumption during production and lower emissions of greenhouse gases. Cold mix asphalt also allows for the use of recycled materials, further enhancing its environmental sustainability. 3. Geotextiles are synthetic materials used in road construction for various purposes such as soil stabilisation, drainage, and erosion control. They can help in reducing the need for excessive excavation and use of natural resources like stone and gravel, thereby minimizing environmental impact. 4. Hot mix asphalt technology involves producing asphalt mixtures at high temperatures. While it provides excellent performance properties for roads, it typically requires higher energy consumption during production compared to cold mix asphalt technology. 5. Portland cement is a key ingredient in concrete production. While it is widely used in construction, its production process is energy-intensive and emits significant amounts of carbon dioxide, contributing to greenhouse gas emissions. Therefore, the correct answer is A. 1, 2, and 3 only.