Answer: Manholes are usually round, primarily because roundness is the best shape to resist the compression of the earth; covers are round because they are easier to manufacture than square or rectangular shapes, they are easier to move by rolling, and they can't fall into the opening.
Explanation:
Answer:
0.2 moles, assuming weight of dried salt
Explanation:
In order to determine the number of moles, we need to be aware of the mass of the substance in question.
Assuming the mass of the dehydrated 
is 50g.
No. of moles = mass of substance/ molar mass of the substance.
= 
= 0.2 moles moles.
Answer:
It is required 0.3 molecules of O2 to produce 0.6 molecules of H2O
Explanation:
The water´s formation reaction is: 2H2 + O2 --> 2H2O
This reaction shows the molecular O2:H2O ratio: 1:2.
Then, if we want to know how many molecules of O2 are required to produce 0.6 of H20, it is necessary calculate as it showed next:
0.6 molecules H2O * (1 molecula O2 / 2 molecules H2O)= 0.3 molecule O2
Explanation:
Algae is a group of a photosynthetic eukaryotic organisms that plays a very important role on the ecosystem. It forms the lower base of the food chain and supports all the life forms of the ecosystem. It takes up water and carbon dioxide from the atmosphere to prepare food during the process of photosynthesis and maintains a balance in the ecosystem.
In the context, if the algae disappears, the fish might die as the small fishes feeds on this algae. This is a concern as the algae is main component of food source and forms the base of the food chain. If there will be no algae there will be no life form on earth, as all species depend on each other to survive.
In order to prevent this from occurring, we must protect our algae. We must plant more trees, keep our water bodies healthy, we should not litter our ponds and lakes. We should also help these algae to grow and survive so that other life forms can feed them and thus maintain the ecosystem.
It will either be B or D, but I don't know about burial.
