Duckweeds will block the sunlight entering the water and thereby decrease the population of submerged plants.
Option B
Step-by-step explanation:
Duckweeds are a deadly weed that grows on the surface of water bodies like lakes and ponds. The population of these plants increase to a huge extent because of the fertilizers that drain into these water bodies from the nearby agricultural fields.This is called eutrophication.
Now these plants form a layer covering the surface of the water bodies. This leads to blocking the sunlight from entering inside the water. This leads to sunlight deficiency inside the water body. Thus the plants that are growing on the bottom of these water bodies cannot get sunlight and thus dies.