The correct answer is A. use a singular verb.
If a noun is singular, but also collective, it means that it has the form of a singular noun, but refers to more than one entity. However, based on the context, it will either take a singular, or a plural verb. 
For example: <em>The team is quite good</em> (where the team is a collective noun referring to all members together) VS. <em>The team are not behaving properly</em> (where this refers to all members individually). 
 
        
                    
             
        
        
        
They are called compound sentences.When 2 sentences are connected.
        
             
        
        
        
Answer:
Use a pair of commas in the middle of a sentence to set off clauses, phrases, and words that are not essential to the meaning of the sentence. Use one comma before to indicate the beginning of the pause and one at the end to indicate the end of the pause. 9 December 7, 1941, will never be forgotten. And lastly use commas when there is a list of 3 or more things.(example) I want you to pick up eggs, biscuits, sausages, and pancakes.
 
        
             
        
        
        
I don't see any following options to answer your questions.