Final answer:
In military etiquette, the word 'etiquette' refers to proper behavior, while 'deference' signifies showing respect. The correct meanings of these words in the given context are behavior and courtesy, respectively.
Step-by-step explanation:
In the sentence 'In the code of military etiquette silence and fixity are forms of deference,' the italicized words have specific meanings. The word etiquette refers to the set of rules or customs that dictate proper behavior in a social or official environment, while the word deference signifies a way of behaving that shows respect for someone or something. Therefore, the correct answer to the meanings of the italicized words is option 4) behavior, courtesy. This means that within the military context, maintaining silence and stillness are ways to demonstrate respect according to military customs.