24. Which of the following word formation processes is incorrect?
(A) Fire station is an exocentric compound.
(B) SCUBA is an acronym.
(C) The creation of the word smog involves blending.
(D) The verb peddle from the older English noun peddler involves back-formation.

Exocentric compound/ headless compound: lacks a head word (兩者無關連)

--> the construction as a whole is not grammatically and/or semantically equivalent to either of its parts.  For instance, a dikbuik fat-belly fat person is not a type of belly, but a person with a fat belly. 
Fat-belly並不是一種belly。

Endocentric compound:  one member functions as the head and the other as its modifier, attributing a property to the head.
The relation between the members of an endocentric compound can be schematized as 'AB is (a) B'. (AB這個詞是B的一種)

-->Example: steamboat as compared with boat is a modified, expanded version of boat with its range of usage restricted, so that steamboat will be found in basically the same semantic contexts as the noun boat.
Steamboat是一種boat。

Back-formation: either the process of creating a new word by removing actual or supposed affixes, or a neologism formed by such a process.
Back-formations are shortened words created from longer words, thus back-formations may be viewed as a sub-type of clipping. 從以前的詞衍生出新的詞，但以前的詞卻不再使用。

exocentric compound 離心結構複合詞
e.g. birdbrain笨蛋     意思與原本的字無關
 endocentric compound 向心結構複合詞 e.g. harmchair  就是指一種chair