The electrons in the outermost shell of the covalent compounds are shared by nearby atoms. As there are no free electrons for conducting electricity, the covalent compounds are perfect insulators at absolute zero. As the temperature increases, some electrons move from valence band to conduction band. This gives rise to conductivity. But as the numbers of charge carriers are very low, covalent compounds are poor conductors. On the other hand metals are good conductors cause of their bonding. Metallic bonding consists of a sea of electrons rather than discreet bonds. The free electrons are able to move freely. Since electricity and heat need electrons to move, the bonding promotes conductivity.
The vitamin that plays an important roles in the epithelia and in the synthesis of visual pigments is vitamin A.
Vitamin A (retinol) is needed for the synthesis of photopigments. The photopigment rhodopsin is synthesized withinside the rods and is answerable for imaginative and prescient beneathneath low ranges of light. When nutritional reassets of diet A are insufficient for a protracted length of time, the quantity of visible pigment withinside the photoreceptors declines.
Vitamin A (VitA) is a micronutrient this is important for preserving imaginative and prescient, selling boom and development, and defensive epithelium and mucus integrity withinside the body.Vitamin A is critical for lots physiological processes, which includes preserving the integrity and feature of all floor tissues (epithelia): for example, the skin, the liner of the respiration tract, the gut, the bladder, the internal ear and the eye.
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B is the answer. But the changes would take over time
Answer:
the tips of the steams and roots, also known as an apices
Pollution from a near by city is your answer ;D