Answer: B) Methane Explanation: The main constituent of biogas is methane (55-70%), CO2 (30-45%) and some traces of gases such as H2S and ammonia. Biogas is produced under anaerobic conditions; the process is denominated as anaerobic digestion.

Answer: A) numbers of neutrons Explanation: Isotopes are variations of an element that have the same charge as the original element, but a different mass, which is caused by either more/less neutrons in the nucleus.

Answer: D) II and III only Explanation: Plagiarism is when you copy someone's work and try to pass it off as your own. Plagiarism can be a violation of copyright laws and can be considered cheating, resulting in you getting a failing grade or even being kicked out of school.

Answer: A) Sulphur dioxide Explanation: Air pollutants are solid particles, gases, and liquid droplets in the air that can adversely affect ecosystems and the health of humans.   Major ambient air pollutants include toxic metals, polycyclic aromatic hydrocarbons, benzene, particulate matter (PM), nitrogen oxides, sulfur oxides, carbon monoxide, and ozone. Power plants, factories, and vehicle and air traffic are the most important anthropogenic sources of air pollution.   In addition, natural sources such as wildfires and volcanic activity contribute to ambient air pollution.

Answer: A) There is extensive intramolecular hydrogen bonding in the condensed phase. Explanation: Water possess intermolecular hydrogen bonding in the condensed phase.   Hence, the given statement 'There is extensive intramolecular hydrogen bonding in the condensed phase.' about water is FALSE.

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.

Answer: D) chromium Explanation: Stainless steel contains 18% chromium and 82% steel