The correct answer is A.
The official guidelines from doctors state that infants should start consuming solid food after the age of six months. In order for the infants to be safe and healthy, they need to be able to sit up, support their back and chew safely before being given solid food.
The lungs are lined with epithelial cells:)
The three most common elements are oxygen, carbon, and hydrogen
Enzyme functioning is very much depends on it;s structure, and if it denatured due to deviation from normal physical conditions, then it won't function properly. Hence, your sentence is "True"
Hope this helps!