OE


B, E From the meaning of the sentence, you can see that the correct answer choices will render the meaning “commercial arsenic usage has diminished, but its ongoing presence is a major health concern.” Because the blank is placed at the start of the first clause, you need a sense of contradiction that gives the meaning “even though.” (A) After, (C) Inasmuch as, (D) Considering, and (F) Because all lack the contradiction you need, leaving only (B) Although and (E) While, which are synonyms of each other and match the prediction.