Question

what is the significance of residual volume of air that lungs always contains

Answer 1

Residual volume is the volume  of air which always be present on the lungs.  Residual Volume is important because it prevents the lungs from collapsing. Even after we have expelled as much air as possible  gaseous exchange is still occurring by residual volume in the lungs.

Answer 2

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$\huge{\boxed{\bold{ANSWER}}}$

During the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbondioxide to be released.

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