A unique feature of diatom cells is that they are enclosed within a cell wall made of silica<span> (hydrated silicon dioxide) called a </span><span>frustule.</span>
Answer:
Ocean and river pollution: it has been solved but the problem is that the machine that filters plastic from the water is making it difficult for Fishermen to catch fishes.
that's the only I can think of that could cause problem
skeletal system is your Answer
hope this help <3
