The sentence "Lightening that strikes the dry forests can cause forest fires" is restrictive: no commas needed. The correct answer is A.
Explanation:
Methemoglobin (metHb) is an oxidized derivative of hemoglobin in which heme iron is in the ferric (Fe3+) or oxidized state rather than the ferrous (Fe2+) or reduced state. Small amounts of methemoglobin normally are formed daily, associated with the release of oxygen from hemoglobin (auto-oxidation).
Methemoglobin cannot bind oxygen, which means it cannot carry oxygen to tissues. It is bluish chocolate-brown in color. In human blood a trace amount of methemoglobin is normally produced spontaneously, but when present in excess the blood becomes abnormally dark bluish brown. The NADH-dependent enzyme methemoglobin reductase (a type of diaphorase) is responsible for converting methemoglobin back to hemoglobin.
Normally one to two percent of a person's hemoglobin is methemoglobin; a higher percentage than this can be genetic or caused by exposure to various chemicals and depending on the level can cause health problems known as methemoglobinemia. A higher level of methemoglobin will tend to cause a pulse oximeter to read closer to 85% regardless of the true level of oxygen saturation. An abnormal increase of methemoglobin will increase the oxygen binding affinity of normal hemoglobin, resulting in a decreased unloading of oxygen to the tissues.
<span>gas production also meant a doubling in the rate of photosynthesis? ... By adding a number of equal volumes of normal sodium bicarbonate
solution the concentration of carbon dioxide available to the plant is
increased and the gas production measured. Prior knowledge. Sodium hydrogencarbonate is a source of carbon dioxide.</span>
