Eutrophication is a process that occurs when excessive amounts of nutrients, particularly nitrogen and phosphorus, are introduced into a body of water. This leads to the overgrowth of algae and other aquatic plants, which can ultimately result in the depletion of oxygen levels and the death of aquatic organisms.

1. Nitrogen:
- Nitrogen is a key component of fertilizers and is commonly used in agricultural practices. When excess nitrogen is applied to fields or washed into water bodies through runoff, it can contribute to eutrophication.
- Nitrogen can also be introduced into water bodies through the discharge of untreated or poorly treated sewage and industrial waste.

2. Phosphorus:
- Phosphorus is another essential nutrient for plant growth, and it is often found in fertilizers and detergents. Like nitrogen, excessive amounts of phosphorus can enter water bodies through agricultural runoff and wastewater discharge.
- Phosphorus is particularly problematic because it tends to accumulate in sediments, where it can be released over time and continue to fuel algal growth even after the initial source of phosphorus has been reduced.

3. Chlorofluorocarbons (CFCs):
- CFCs are a class of synthetic chemicals that were historically used in a variety of applications, including as refrigerants and aerosol propellants. While CFCs are not directly associated with eutrophication, they have been linked to other environmental issues such as ozone depletion.
- Eutrophication is primarily driven by the excessive input of nutrients, particularly nitrogen and phosphorus, rather than by the presence of CFCs.

In conclusion, substances that contribute to eutrophication include nitrogen and phosphorus, which are commonly found in fertilizers, agricultural runoff, and wastewater discharge. Chlorofluorocarbons (CFCs) are not directly associated with eutrophication. Therefore, the correct answer is option 'A' (1 and 2 only).