D, It's ACRONYM, not ABBREVIATIONS.

ac⋅ro⋅nym
a word formed from the initial letters or groups of letters of words in a set phrase or series of words, as Wac from Women's Army Corps, OPEC from Organization of Petroleum Exporting Countries, or loran from long-range navigation.

ab⋅bre⋅vi⋅a⋅tion
a shortened or contracted form of a word or phrase, used to represent the whole, as Dr. for Doctor, U.S. for United States, lb. for pound.