Everyday Science

Helium is used as a substitute for nitrogen in breathing gas mixtures for deep sea divers to prevent nitrogen narcosis and reduce breathing resistance under high pressure. Argon, xenon, and krypton are not commonly used for this purpose due to their physical properties and cost.

The vernal equinox in the northern hemisphere occurs around March 20-21 and marks the beginning of spring, when day and night are approximately equal in length.

Pellagra is a nutritional deficiency disease caused by a lack of niacin (vitamin B3) in the diet. Albinism is a genetic condition, cirrhosis is a liver disease often caused by alcohol abuse or hepatitis, and rabies is a viral infection, so they are not nutritional deficiency diseases.

Mercury, Venus, Earth, and Mars are called terrestrial planets because they have solid rocky surfaces, unlike gaseous planets which are composed mainly of gases. They are not dwarf planets, which are smaller bodies like Pluto.

Amnesia is a condition characterized by the loss of memory, which directly relates to option D. It does not involve sleeping sickness, loss of sight, or loss of hearing.

The ELISA (Enzyme-Linked Immunosorbent Assay) test is primarily used to detect antibodies in the blood, such as those produced in response to HIV infection, making it a key diagnostic tool for AIDS. It is not used to directly detect coronavirus, tuberculosis bacteria, or cancer.

Earth is known as the 'Watery Planet' because it has abundant liquid water covering about 71% of its surface, which is essential for life. None of the other planets have such extensive water bodies.

Vitamin B1 is commonly known as Thiamine. The other options correspond to different vitamins: Riboflavin is Vitamin B2, Retinol is Vitamin A, and Niacin is Vitamin B3.

Milk typically has a slightly acidic pH around 6.5 due to the presence of lactic acid and other components, making option B the correct answer.

Ophthalmology is the branch of medicine that deals with the anatomy, physiology, and diseases of the eye. The other options relate to different medical fields: Obstetrics deals with childbirth, Physiology studies body functions, and Haematology focuses on blood.