In the sentence, the modified adverb clause is
letter C: rice
Adverb clauses or phrases are group of words used
in shifting or adding meaning of a verb, clause, adjective, or another adverb.
These clauses can be used if: firstly, a sentence contains a subject and a
predicate. Secondly, when a subordinate conjunction is used and thirdly, if it
answer the ‘adverbial questions’ – when, why, when and how. It is also further
categorized to time, place, manner, degree, condition, concession and reason
