Correct answer # 2: The world's nations must cooperate; one nation cannot solve the world's problems by itself.
When you connect two related independent clauses or sentences you use a semicolon. Both sentences should be completed grammarly writtend and with a connection. Make sure you do not write a capital letter after the semicolon, unless it is a proper name. 
Answer # 3 is incorrect as there is a capitalized word
Answer # 1 it is incorrect to use "for" as the sentence is grammarly completed
 
        
             
        
        
        
Answer:
In works of art, macabre is the quality of having a grim or ghastly atmosphere. The macabre works to emphasize the details and symbols of death. 
 
        
             
        
        
        
Who is jimmy ? We need information about the story and everything else so we can answer your question !!
        
             
        
        
        
The answer is D, because she’s helping her.
        
                    
             
        
        
        
Singular- "earth's" is singular because its showing ownership
plural- "features" is plural because its saying that there is more than one feature of the earth