Does it ever frustrate you that you’ve spent most of your career being engaged in a Sisyphean battle? The underlined word can be replaced by （）.

Does it ever frustrate you that you’ve spent most of your career being engaged in a Sisyphean battle? The underlined word can be replaced by （）.
A.futile　
B.demanding
C.deceitful
D.frustrating
正确答案：futile