Answer:
The option that is a key detail about Franklin's employment in the excerpt is:
D. Benjamin Franklin worked at the “New England Courant.”
Step-by-step explanation:
Let's work with elimination to find the correct answer. The question is about Franklin's employment, his job, which means we should ignore, so to speak, details that are not related to this topic.
Letter A concerns Franklin's position in the family. He was the youngest of seventeen children. That has nothing to do with employment, so we can eliminate letter A.
Letter B concerns employment, but it is Franklin's father's job, not his. We can also eliminate it.
Letter C concerns Franklin's education, which was finished when he was only 10. We can also discard this option.
Finally, we are left with letter D, the correct option. It speaks of Franklin's job at the publishing house for the "New England Courant".