6875. He was warned at the outset of his career.

✅ The correct answer is option B.
End : a final part of something, especially a period of time, an activity, or a story.

Beginning : the point in time or space at which something begins.

Middle : the point or position at an equal distance from the sides, edges, or ends of something.

Entrance : an opening, such as a door, passage, or gate, that allows access to a place.

Outset : the start or beginning of something.

Synonym of Outset is Beginning