Iron is the metal found in blood. It is an essential mineral that plays a key role in transporting oxygen from the lungs to the rest of the body and carrying carbon dioxide back to the lungs to be exhaled. Iron is a crucial component of hemoglobin, a protein in red blood cells that binds to oxygen and gives blood its red color. Without sufficient iron, the body cannot produce enough healthy red blood cells, leading to iron-deficiency anemia, a common nutritional disorder.

Methane is the gas that can cause explosions in coal mines. Methane is a highly flammable gas, and when it accumulates in high concentrations in confined spaces like coal mines, it poses a significant risk. Methane explosions can occur if the gas comes into contact with an ignition source, such as a spark or flame, leading to a dangerous explosion. That's why proper ventilation and safety measures are crucial in coal mines to prevent methane buildup and potential explosions.

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.

The plants that never produce flowers are called "cryptogams." Cryptogams include plants such as ferns, mosses, liverworts, and algae. Unlike flowering plants (angiosperms), which reproduce through seeds enclosed within flowers, cryptogams reproduce through spores and do not produce true flowers. Cryptogams are considered more primitive in evolutionary terms compared to angiosperms, which are the most dominant group of plants on Earth today.