The most likely explanation for the variation is the offspring were produced from different combination of genes. A single pair of gold fish mentioned in the question means a male and a female gold fish. The two of them mated and contributed different genes to the fertilized fish eggs, this results in production of various body shape and colouration which is known as variation.
        
             
        
        
        
<span>Neils Bohr </span>developed a model of the atom (Bohr model) to explain how the structure of the atom changes when it undergoes energy changes. His major idea was that energy of the atom was quantized (this means that the atom could only have very specific amounts of energy) and the amount of energy in the atom was related to the electrons possession in the atom. In the Bohr model, electrons travel in orbits around the nucleus. The further the electron from the nucleus the more energy it has. Bohr used Planck's quantum concept of E=hv.
        
             
        
        
        
The common name of this organism is hydra.
<u>Explanation:</u>
Hydra is a fresh water organism and belongs to the phylum Cnidarian. They have tentacles around their body that enables locomotion as well as protection from prey.  Hydra has the ability of regeneration and the asexual mode of reproduction in hydra is budding.
In the budding process, a small bud develops in the parent body and the bud after maturation gets detached from the parent body and grows into a new individual.  Sexual mode of reproduction is also found in hydra.
 
        
                    
             
        
        
        
Answer:
Explanation:
Aldosterone is a hormone which is produced by the adrenal glands which are present above the kidneys. The role of aldosterone is to regulate the blood pressure. It causes the reabsorption of water and salts into the bloodstream during the kidney filteration process. Hence, maintains the blood volume, restors blood pressure and salt level.
Renin is an enzyme. It facilitates chemical reactions which stimulates the synthesis of angiotension II, it directs the synthesis of aldosterone. 
 
        
             
        
        
        
Answer:
A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere. So i think its True