Answer:
A. He has a large buildup of lactate in his muscles.
Explanation:
Ideally, our body cells, via the process of aerobic cellular respiration, need oxygen to break down glucose. However, during rigorous activities or exercises, oxygen can become unavailable for use. In this case, the body cells switch to use another way of cellular respiration, which is FERMENTATION. 
This fermentation causes a build up of lactic acid/lactate (its byproduct) in the cells of the muscles being used, which physically causes a burning and aching sensation just as the case of this hiker. The climbing of the steep path is causing causing the fast usage of oxygen in his cells.
 
        
             
        
        
        
<span>The answer is letter B. The formation of the three geminal layers and the primitive gut. The formation of gastrula starts when the cells starts folding in blastula slowly forming into a blastopore, that results to a double layer cup cell, forming the geminal layers and the primitive gut </span>
 
        
                    
             
        
        
        
Answer: I couldn't find the site, but I can tell you what each of these men, that way you can find them on your own :)
Explanation: 
Using a bullfrog as an example
Their common name is Bull frog, their scientific name is Lithobates catesbeianus
Major physical structures and color are: Strong legs for jumping, buldge-y eyes, slick skin. They are usually greenish brown.
Oops. I just saw the Siberian wood frog bit.
I need to go, but I hope my bullfrog example will help you answer your questions for Siberian wood frog. :)
 
        
             
        
        
        
I don't know how specific you need to get for this question. The basic answer would be the mitochondria as it is where the Krebs Cycle, the Electron Transport Chain, and Chemiosmosis (also referred to as oxidative phosphorylation) all occur. Chemiosmosis is where the majority of ATP is produced during cellular respiration, and it primarily occurs in the matrix of the mitochondria as protons move down the gradient through ATP Synthetase channels.