Even though there is no word in bold, the complement is formed by a single word: “popular.” Thus, we can assume that the word that should be in bold is “popular.”
Answer:
Predicate adjective
Explanation:
A predicate adjective is an adjective that modifies or describes the subject of a sentence and that is placed after a linking verb. Linking verbs are those expressing conditions or states (not actions), like the verbs "to be," "to become" and "to seem." In the sentence, “popular” is a predicate adjective because it follows the linking verb “is” and it describes the subject “The roller-coaster.”
