ANSWER:
D. Using historical research ensures that you create original work and use appropriate details.
This will ensure that you are aware of historical facts and so don't produce work which is similar or the same as what is written in the past. As well as this, it will ensure that you are respecting the details and facts of historical events and that your work makes sense.
        
             
        
        
        
When he wrote This excerpt he was referring to knowledge, he said that he reads a book a day and that knowledge was his banknote that got him so far,
        
             
        
        
        
The preposition in the given sentence "Gracie and Helen had not seen each other for 50 years" is 'for'.
<h3>What is a preposition?</h3>
A preposition is a word or phrase that appears before a noun, pronoun, or noun phrase to indicate direction, time, place, location, spatial relationships, or to introduce an object. 
Prepositions include words like "in," "at," "on," "of," "to", etc.
Thus, the preposition in the given sentence "Gracie and Helen had not seen each other for 50 years" is 'for'.
For more details regarding preposition, visit:
brainly.com/question/4956879
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