Answer
The answer and procedures of the exercise are attached in the following archives.
Explanation  
You will find the procedures, formulas or necessary explanations in the archive attached below. If you have any question ask and I will aclare your doubts kindly.  
 
        
             
        
        
        
A) Opportunity cost
because an opportunity cost is for example you have to pick from a xbox one or a ps4. You saw that the ps4 was more scarce for you but you had to give up the xbox one to obtain the ps4. Nothing is free in life!!! You sacrificed the xbox one for the ps4
        
             
        
        
        
B. Employers are willing to pay more for those skills.
        
             
        
        
        
Answer:
The answers are, 
For A. It's the revenue recognition principle in which revenue is recognised when it is earned, now when the cash is realized.
For B. Its the matching concept in which all expenses related with earnings are debited against it to find the profit or loss.
For C. It's full disclosure principle in which all events in material nature has to be disclosed. We can say that going concern effects this as well, as if any event affect the continuity of an entity, it has to be disclosed as well.
For D. It's the historical cost principle in which you account the assets and expenses at the price you paid for them. When the value increases over time, you can reevaluate and adjust it.
Explanation:
 
        
             
        
        
        
Answer: (C) Perceptual mapping
Explanation:
  The perceptual mapping is one of the type of technique that is used by the marketers for visually displaying the different types of perceptions of the consumers and the users. 
 It is also known as the market mapping technique that is used for the developing the various types of brands and the products in the market for based on the customer perspective.  
 According to the given question, the Apex corp. is using the perpetual mapping technique for determining the different types of product attribute in the market.  
  Therefore, Option (C) is correct answer.