To make a singular noun, “octopus,” possessive, you should
a. add an apostrophe followed by s.
b. add an s followed by an apostrophe.
c. add an es.
d. add just an s.

true. the definition explains it: a word or phrase that modifies or qualifies an adjective, verb, or other adverb or a word group, expressing a relation of place, time, circumstance, manner, cause, degree, etc. this is a dictionary definition that i have looked up in a dictionary.

abater   ambary   ambery   baryta   baryte   bemata   betray   jarvey   ramate   ramjet

explanation:

those are all the possible words