题干
_______he had failed many times, he didn't give up and succeeded in the end.
A：Unless
B：Although
C：If
答案(点此获取答案解析）
B
_______he had failed many times, he didn't give up and succeeded in the end.
A：Unless
B：Although
C：If
时，不等式
恒成立，则实数
的取值范围是（ ）