The right answer is a)
The context for each document you write directly affects how you have researched your topic and what media is employed to deliver the message.
When writing it is necessary to give key elements in order to provide new concepts,and words to develop thoughts. This information illuminates the meaning and relevance of the text and can be about,historical,cultural,social or political events.
Context matters, for it informs the reader the ocassion or situation in which a document was written and specially, how it was written.
for example "Animal Farm" by George Orwell. The events in the book take place in a farm where the animals have frequent disputes.
The reader would need to be put in context to know that the animals represent political figures of the former Soviet Union.
This is when context comes in handy.