Ecology is the study of the relationships between living organisms, including humans and their physical environment. The German scientist Earnst Haeckel was the first to use this word in 1869.

Acetylene is the only fuel gas suitable for gas welding because of its favourable flame characteristics of both high temperature and high propagation rates. Other fuel gases, such as propane, propylene or natural gas, produce insufficient heat input for welding but are used for cutting, torch brazing and soldering.

Answer: B) Cellulose Explanation: Carbohydrates are also called as saccharides are molecular compounds made from just three elements: carbon, hydrogen and oxygen.   Carbohydrates are: * a source of energy for the body e.g. glucose and a store of energy, e.g. starch in plants * building blocks for polysaccharides (giant carbohydrates), e.g. cellulose in plants and glycogen in the human body * components of other molecules eg DNA, RNA, glycolipids, glycoproteins, ATP   Types: 1. Monosaccharides (e.g. glucose) and 2. Disaccharides (e.g. sucrose) are relatively small molecules. They are often called sugars. 3. Other carbohydrate molecules are very large called Polysaccharides such as starch and cellulose.