This given definition of "-ment" is useful to know because -ment functions as a suffix. Thus, the correct option is A.
The suffix may be defined as a part of any root word that is added to the end of it. For example, Adjustment ⇒ -ment is a suffix, and Sadness ⇒ -ness is a suffix.
Therefore, the correct option for this question is A, i.e. suffix.
To learn more about Suffix, refer to the link:
https://brainly.com/question/513403
#SPJ1