Explanation:
AswerB
hydrogen, helium and lithium
It took 380,000 years for the electrons to be trapped in orbits nuclei forming the first atoms. (which is option B)
The correct answer is A. Decline in vision
Explanation:
The term "middle age" is used to describe the time span between 45 and around 65 in human life. During this, important changes occur in terms of senses, this age usually implies a decline in senses including pain, taste, smell, and vision. In terms of vision, it is common during middle ages people began experiencing blurring vision or weakened vision as during this age conditions such as presbyopia, glaucoma, cataracts, among others. Additionally, the decline in vision in this age is commonly related to other conditions such as diabetes, the use of medicines and also jobs that are visually demanding. Thus, in middle age, people commonly experience a decline in vision.
The Mitral valve which is also known as left atrioventricular prevents blood movement from left ventricle to left atrium.
Explanation:
- Human heart is four chambered.
- Two of these are receiving chambers known as atria and the other two are distributing chamber known as Ventricles.
- Atria are superior chambers and ventricles are inferior chambers.
- The heart has four valves broadly grouped as Atrioventricular valves and Semi lunar valves.
- Atrioventricular valves allows flow of blood from atria to ventricle. These are tricuspid valve and bicuspid valve.
- Semi-lunar valves allow blood to pass out of the heart. These include the pulmonary and aortic valves.
- The pulmonary valve allows blood to flow from right ventricle to the heart while aortic valve allows blood to flow from left ventricle to the Aorta.
- The Tricuspid valve located between the right atrium and right ventricle allows blood to flow from right atrium to the right ventricle.
- The Bicuspid valve ( Mitral valve) located between the left atrium and left ventricle allows the blood flow from left atria to left ventricle.
- Valves maintain the unidirectional flow of blood and thus prevent its back flow.
