Answer:
A. Soberly.
Step-by-step explanation:
The word soberly is not an unfamiliar word, so it is the least likely entry word.
The other words,
Frigate
Expedite
Streamer
While they are not entirely unfamiliar, but they would most likely be entry words to be looked up in a dictionary.
The word "soberly" is gotten from the word "sober" which means different things but the most common meaning would be, "unaffected by alcohol" and it is a word that is familiar to many speakers of the English language.