Which of the following is a subordinate adverb? Select all that apply.

if

after

therefore

whenever

Among the choices, if, after and whenever are considered to be subordinate adverbs while therefore is not a subordinate adverb. Because subordinate adverb is define as those adverbs that connect two adverbial clauses. An adverbial clause is commonly, but not always, fronted by a subordinate conjunction-sometimes called a trigger word.