Biology

Oxygen is the most abundant element in the human body by percentage, followed by carbon. Calcium and hydrogen percentages given are incorrect or misleading. Carbon makes up about 18% of the human body, making it the second most abundant element after oxygen.

Emphysema is a common respiratory problem caused by smoking, characterized by damage to the air sacs in the lungs, leading to breathing difficulties. While tuberculosis, asthma, and cancer can affect smokers, emphysema is most directly linked as a common smoking-related respiratory disease.

Water-soluble vitamins include the B-complex vitamins and vitamin C, which dissolve in water and are not stored in large amounts in the body. Vitamins A, D, and K are fat-soluble, not water-soluble.

Each human kidney contains approximately 1 million nephrons, which are the functional filtration units responsible for producing urine.

The percentage of blood cells, specifically red blood cells, in human blood is approximately 45%, known as the hematocrit value. This is a standard physiological measure.

Humpback whales produce the loudest sounds among living creatures, with calls that can reach up to 188 decibels, far louder than donkeys or monkeys. This makes option C the correct answer.

Jaundice is a condition characterized by yellowing of the skin and eyes due to high bilirubin levels, which is primarily caused by liver dysfunction or disease.

An octopus has one central brain and eight smaller brains, one in each arm, totaling nine brains. This unique nervous system allows each arm to operate with a degree of independence.

Pomology is the branch of botany that studies fruit and fruit cultivation, making 'Fruits' the correct answer.

Vaccination involves introducing a weakened or inactive form of a pathogen to stimulate the body's immune system to produce its own antibodies, which is characteristic of artificial active immunity.