TOEIC・English Undergraduate about 2 yearsago

theの後ろに名詞が来るのはわかるのですが、AとC両方とも名詞ですよね？なんでAが答えなんですか？

121. Employees traveling to foreign countries will receive travel allowances reflecting the ----- in local currency. (A) equivalent (B) equivalently (C) equivalence (D) equivalency