The correct answer is 4. transform.
According to structural grammarians, who, as the name itself suggests, study the structure of grammars, there are 12 types of words, some of which include adjectives, nouns, verbs, etc. In the list above, we can immediately see that adjectives and nouns fall under the category of morphological classifications.
Auxiliary mostly refer to auxiliary verbs, such as to be, to have, etc. which are used to form various tenses.
The only option that is not one of the morphological classifications is transform.