When the inspiratory muscles relax, the rib cage returns to its original position as a result of:. a) gravity.
b) exhalation.
c) elastic rebound.
d) partial pressure difference.
e) accessory muscle contraction.

The correct answer is c) elastic rebound.

Explanation:

When the muscles are relaxed (end of expiration) the lung and the chest wall act in opposite directions, the lung tries to reduce its volume due to the inward retraction of the alveolar walls and the chest wall tends to increase in volume due to elastic expansion, these opposing pressures are responsible for keeping the alveolus partially open (functional residual capacity). The muscles of inspiration act by increasing the volume of the thoracic cavity causing the intrapleural pressure to become lower (Boyle's law), the intraalveolar volume increases and then the intralveolar pressure decreases below atmospheric (negative) and flow is generated towards the lung expanding it, that is, during inspiration, the diaphragm contracts moving downward, allowing the rib cage to widen and air into the lungs.

hey bro i looked it up on google the structure of the eye-spot in euglena viridie, e. ehrenbergii, and phacus pyriyorme is not as franzé haa described it. the so-called “crystal body” and “lens bodies” were not found in any of the individuals of the species examined by me. as earlier observers have stated, the eye-spot consists simply of a mass of pigment granules arranged in a single layer, and probably embedded in a protoplasmic framework, but the latter could not be seen, and its presence was only inferred from the fact that the pigment granules must be held together in some way, thd the eye-spot as a whole is capable of expansion, and that the pigment granules can be separated from each other.

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