Why do deep-sea divers carry oxygen cylinders for respiration?

Read the following and answer the questions from $(i)$ to $(v)$.
We need energy to perform various activities. This energy is derived from the catabolism of various components of food, e.g., proteins, carbohydrates, fats, etc. Oxygen is required for catabolic processes and carbon dioxide is released in the process. So, the body requires a continuous exchange of gases; oxygen from the atmosphere is taken inside, and carbon dioxide produced is given out. In human beings, a respiratory pigment called hemoglobin present in RBCs has a very high affinity for oxygen. In tissues, the exchange of gases occurs between oxygenated blood and tissue cells.
$(i)$ People living at sea level have around $5$ million RBCs per cubic millimetre of their blood, whereas those living at an altitude of $5400$ metres have around $8$ million. This is because at high altitude:
$(a)$ People eat more nutritive food, therefore more RBCs are formed.
$(b)$ People get pollution-free air to breathe and more oxygen is available.
$(c)$ The partial pressure of oxygen $(PO_2)$ is low, and hence more RBCs are needed to absorb the required amount of $O_2$ to survive.
$(d)$ There is more $UV$ radiation which enhances $RBC$ production.
(ii) The given graph illustrates the changes in lung volume during the process of breathing. The change from $II$ to $III$ indicates:
$(a)$ Movement of the diaphragm away from the lungs.
$(b)$ Expansion of the thoracic cavity.
$(c)$ Movement of air out of the lungs.
$(d)$ Expansion of ribs.
(iii) Which one of the following is a possibility for most of us in regard to breathing, by making a conscious effort?
$(a)$ One can breathe out air totally without oxygen.
$(b)$ One can breathe out air through the Eustachian tube by closing both nose and mouth.
$(c)$ One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all.
$(d)$ The lungs can be made fully empty by forcefully breathing out all air from them.
(iv) Refer to the given figure and answer the following matching question:
$(I)$ Are the actual sites of respiratory gas exchange?
$(II)$ Is the common passage for air and food?
$(III)$ Is provided with incomplete cartilaginous rings?
$(IV)$ Relaxes and gets back to its original shape during expiration?
$(V)$ Moves upwards and outwards during inspiration?
$(a)$ $(I) - s, (II) - p, (III) - q, (IV) - r, (V) - t$
$(b)$ $(I) - r, (II) - p, (III) - q, (IV) - s, (V) - t$
$(c)$ $(I) - t, (II) - q, (III) - r, (IV) - s, (V) - p$
$(d)$ $(I) - p, (II) - q, (III) - r, (IV) - s, (V) - t$
$(v)$ Which of the following sequences is correct to initiate inspiration?
$(I)$ The contraction of intercostal muscles raises the ribs and sternum.
$(II)$ Volume of thorax increases.
$(III)$ Intrathoracic pressure of the lungs decreases.
$(IV)$ Diaphragm contraction.
$(V)$ Air rushes into lungs.
$(a)$ $(I), (II), (IV), (V), (III)$
$(b)$ $(I), (II), (III), (IV), (V)$
$(c)$ $(I), (IV), (II), (III), (V)$
$(d)$ $(V), (I), (II), (III), (IV)$

In which of the following organisms does gaseous exchange during respiration not take place through the cell membrane or skin?

$(i)$ Under normal conditions, what is the rate of breathing per minute for an adult? (ii) Why does the rate of breathing increase significantly during vigorous exercise?

The correct sequence of anaerobic reactions in yeast is:

The portion of the human respiratory tract known as the sound box is: