Why do remoras attach themselves to sharks? a to hitch a free ride, b to gain access to free food, c to avoid getting eaten by other fish, d all of the above.

Lysosomes contain digestive enzymes (lysozyme) and in digestion of different biomolecules like proteins, fats, starch, etc.cleans the cell by destroying damaged organellesprotects cells from certain virus/bacteria by killing them

Sand and gravel would be the answer

Lakes and ponds follow a natural life cycle process, which is known as eutrophication. this process happens when nutrients are continuously added to the pond, in this case, through continuous fertilizer run-off.  over time, the pond would undergo these eutrophication  stages: oligotrophic, mesotrophic and eutrophic.continuous fertilizer run-offs would also lead to the continuous supply of nutrients to the pond. in the process, it will allow not just the algae, but also the other organisms to thrive in it.  in the long run, the pond would reach the eutrophic stage and will be silted and will have low water clarity, high algae and nutrient concentration and very low dissolved oxygen concentrations.if the situation won't be interrupted, in the long term,  the fishes will no longer thrive in the pond as eventually, it would disappear into a marshland, then into a forest land-- as the pond finally reaches the end of its life cycle.