He was warned at the outset of his career.

The correct answer is B. beginning.

The word “outset” means the beginning of something. In this case, it is referring to the beginning of the man’s career.

The other options are incorrect because they do not refer to the beginning of something.

• A. end – The end of something is the opposite of the beginning.
• C. middle – The middle of something is the point between the beginning and the end.
• D. entrance – The entrance to something is the way in.

I hope this helps! Let me know if you have any other questions.