He is in the habit of talking superfluously.

The correct answer is B. needlessly.

To talk superfluously means to talk more than is necessary, or to talk about things that are not important. It is often used to describe someone who talks a lot without saying anything of substance.

The other options are incorrect because they do not accurately describe the meaning of the word “superfluously”.

• A. continuously means without stopping. This does not necessarily mean that someone who talks continuously is talking superfluously.
• C. fluently means easily and smoothly. This does not necessarily mean that someone who talks fluently is talking superfluously.
• D. authoritatively means in a confident and commanding way. This does not necessarily mean that someone who talks authoritatively is talking superfluously.

In conclusion, the correct answer is B. needlessly.