The word "stealthily" means to do something in a secretive or cautious manner, trying not to be noticed.

To choose the option nearest in meaning to "stealthily" from the given options, we need to find a word that conveys a similar sense of being quiet and cautious.

Option D, "quietly," is the closest in meaning to "stealthily. " Both words describe a manner of movement or action that is done without making much noise or attracting attention.

Option A, "briskly," means to do something quickly and energetically. This is the opposite of the meaning of "stealthily. ".

Option B, "boldly," means to do something in a confident and fearless manner. This does not convey the same sense of caution and secrecy as "stealthily. ".

Option C, "wearily," means to do something in a tired or exhausted manner. This does not convey the same sense of caution and secrecy as "stealthily. ".

Therefore, the correct answer is option D, "quietly. ".