Which of the Following Is the BEST Explanation of Where

Which of the following is the BEST explanation of where background details should go in a routine message, and why they should be placed there?

A) Background details should be presented right in the opening, so that readers will have enough context to understand the main point of the message
B) Background details should be presented right in the opening, to show readers that the writer is thorough
C) Background details should be presented shortly after the opening, to provide extra information that supports the main point of the message (which is identified in the opening)
D) Background details should be presented at the end of the message, so that readers who are uninterested in them can easily skip them