The correct statements are sensors in the brain predict the lack of oxygen and the muscles in his body require more energy and thus more oxygen.
Whenever one goes on a level very high from the Earth's surface like in mountains, the sensors in the brain finds out that there is less oxygen present at a higher level. Secondly, whenever a person performs some kind of strenuous activity like mountain trekking, the production of lactic acid takes place in the muscles. Thus, the body needs more oxygen at that time to fulfill the requirement, due to the two mentioned factors the person breathes heavier.
1. electrical signals travel toward the heart. 2. signal received by the atrioventricular node. 3.signal by the nodes in the atrium. 4.the atria contracts. 5. signal transferred to the ventricles. 6. the ventricles contract.
Although earthquakes often occur before a volcaniceruption, they are not the cause. The earthquakes are the result of magma (molten rock) moving underground leading up to an eruption. A few volcaniceruptions are thought to have been triggered or initiated by earthquakes, but this is not the typical case.
