___we tried hard,our efforts ended in failure.but we won't g

題目：

___we tried hard,our efforts ended in failure.but we won't give up.
a,unless.b,if only.c,although.d,because.

解答：

選C
儘管我們已經很努力了,但是我們的努力還是失敗了.但是我們不會放棄.
其他選項意思均不符.