D ) A subject is necessary to finish this sentence. In D ) , “casein” is the subject of the sentence, even if accompanied by a noun phrase enclosed in commas that further more identifies the topic. We don’t know whether mining for means in Area would be extra cost-powerful https://findsomeonetowritemytoefl68916.ampedpages.com/facts-about-can-someone-take-do-toefl-exam-revealed-54716129