Assertion
Deep-sea divers carry oxygen cylinders with them.
Reason:
The deficiency of oxygen in bottom waters changes the type of organisms. Also, they are mostly small and fast-growing in the control rate. Low concentrations of oxygen at the bottom only bacteria and fungi can survive.
A.Both assertion and reason are correct and a reason is a correct explanation for the assertion.
B.Both assertion and reason are correct, but the reason is not the correct explanation for the assertion.
C.The assertion is correct, but the reason is incorrect.
D.Both assertion and reason are incorrect.

Hint: This question can be understood by the concept of pressure and the solubility of the atoms in water and air. As pressure increases the solubility of atoms in water and air decreases. Now we understand this question. We need to know where the pressure is minimum and where the pressure is maximum.

Complete answer:
In mountains, the pressure decreases and therefore the amount of oxygen dissolved in the air also decreases and hence we need oxygen pumps if we are climbing such high altitudes. While going down in the sea, the pressure decreases when we go deep into the sea levels. And therefore the oxygen dissolved in the water also decreases and hence a deep-sea diver needs oxygen cylinders with them to get a sufficient amount of oxygen down in the sea. Due to this deficiency of oxygen, because of the low pressure, the organisms also change their types when they are in the bottled waters. They are small in size because of insufficient oxygen and grow fast. They can tolerate all the low concentrations of oxygen. Therefore, down there only bacteria and fungi can survive in the low oxygen context. Now, in the assertion, we’re provided, the fact that deep-sea divers need oxygen cylinders when they dive in the sea. But the reason is not the correct answer for the assertion. As the correct reason for the assertion is the decrease is pressure down in the sea which decreases the solubility of oxygen in the water.

Note:
Pressure also plays an important role in the temperature and time of cooking. The greater the pressure, the less time it takes to cook the food. For example, it is quicker to cook rice in a pressure cooker than in other utensils.