Answer:
The correct answer is- d. Phosphates
Step-by-step explanation:
Phosphates contain phosphorus which is present naturally in water bodies like lakes. When the amount of phosphorus increase in the stagnant water bodies it makes a suitable environment for overgrowth of weeds which covers the water surface.
Phosphorus is used as a constituent in fertilizers so when this fertilizer reaches water bodies through rain or runoff then it increase the phosphorus level in water which allow the weed to grow exponentially and cause weed problem. Therefore the most likely cause of this weed problem is phosphates.