How many statements are correct?

Question

Read the following statements :

A) Mammalian lungs are solid and spongy

B) In embryo state breathing rate and residual air are absent

C) Residual volume is expelled only by force full expiration

D) Partial pressure of oxygen in expired air is more than in inspired air

How many statements are correct ?

1. 3

2. 4

3. 2

4. 1

Answer 1

I think that option 4 is correct

because mammalian lungs are not solid(they contain air sacs = alveoli) but they are spongy,

statement 2 is correct for that you have to read sub-topic circulation in foetus of std 12 combining with concepts of respiration and circulation of std 11

statement 3 is wrong as residual volume is never expelled out of body,we can expell on expiratory reserve volume through forceful respiration as if we expire RV then there will be vacuum created in lungs and they will collapse

statement 4 is also wrong

Comments

But answer is option 3
That is 2 statements are correct.

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So they have considered  lungs as solid structure.
thats why answer given in some reference books is 2

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OK thank you