The correct option is A Workers in grinding and stone-breaking industries may suffer from lung fibrosis.
In certain industries, especially those involving grinding or stone-breaking, so much dust is produced that the defense mechanism of the body cannot fully cope with the situation. Long exposure can give rise to inflammation leading to fibrosis (proliferation of fibrous tissues) and thus cause serious lung damage. Hence, this is the correct answer.
CO2 carried by haemoglobin as carbamino-haemoglobin is about 20-25 per cent of the total CO2 carried.
Cigarette smoking always leads to bronchitis, and since the option says "may". Hence option C is not the correct option.
Neural signals from the Apneustic center in pons region of the brain can increase the duration of inspiration. Pnemotoxic center limits the rate of inspiration.