The correct answer is option 1: Toxic matters are magnified.

Bio-magnification refers to the process by which toxic substances or pollutants become increasingly concentrated as they move up the food chain. This means that as organisms consume smaller organisms, the concentration of these toxins in their bodies increases.

Option 2, living beings are magnified, is not the correct explanation of bio-magnification. It is the concentration of toxic substances that is magnified, not the organisms themselves.

Option 3, light is magnified, is not relevant to the concept of bio-magnification. Bio-magnification is related to the increase in concentration of toxic substances, not the magnification of light.

Option 4, food is magnified, is not a accurate explanation of bio-magnification. It is the concentration of toxins that is magnified, not the food itself.

Therefore, the correct answer to the question is option 1: Toxic matters are magnified.