D. #4 is the correct answer
<u>Calcium carbonate:</u>
The calcium carbonate is found in sea shells and the bones of sea creatures. And it is settled on layer of ocean. The pH level can be equilibrium with atmospheric 
. There is constant concentration of in the water.
The limestone and calcium carbonate is present in the rocks, streams, lakes is helps to maintain the constant pH in the minerals present in the rock react with excess acid in the water.
When the acids or bases react with the calcium carbonate ,there is the excess change in the pH. The mixture of calcium carbonate ions in the water to prevent the damage in acid rain.
An organized way to collect and record scientific observation using a Hypothesis
Explanation:
Hypothesis is known as initial building block in scientist method. Hypothesis is written in the form of statement. It is based on theories and knowledge. It is proposed between two variables and is mainly classified as independent and dependent hypothesis.
There are six forms of hypothesis. They are simple, complex, Empirical, Null. Altered, Logical and statistical. Relation between two variable predictions is simple hypothesis. On the other side complex hypothesis is the relationship between two or more variables.
Answer:
Both ammonia and chlorine are soluble in water and hence, would dissolve in water if substance X is water and could not be collected. Ammonia gas would react with concentrated sulphuric acid to produce a salt and as ammonia is less dense than air, it should not be collected via a downwards delivery method.
The mechanics of cytokinesis are not yet completely understood, but a great deal is known about the critical timing of its events and other aspects of the final step in the cycle of any one cell. The four stages of cytokinesis are initiation, contraction, membrane insertion and completion .
