This is a fundamental constant in chemistry that represents the number of atoms or molecules in one mole of a substance. (Option 4 is correct) Its value is approximately 6.022 x 10²³, and it is denoted by the symbol "N_A". Avogadro's number is a key concept in stoichiometry. The branch of chemistry deals with the quantitative relationships between reactants and products in chemical reactions.

INS Virat is a Centaur class aircraft carrier currently in service with the Indian Navy. INS Virat is the flagship of the Indian Navy the oldest carrier in service. Virat is currently the second largest ship in the Indian Navy after the INS Jyoti Viraat was completed and commissioned in 1959 as the Royal Navy’s HMS Hermes and was transferred to India in 1987.

Dolly (5 July 1996 – 14 February 2003) was a female domestic sheep, and the first mammal cloned from an adult somatic cell using the process of nuclear transfer.

Vitamin D is often referred to as the "sunshine vitamin" because our bodies can produce it in response to sunlight exposure. When our skin is exposed to sunlight, it synthesizes vitamin D, which is important for bone health and various other bodily functions.