“奏效的”的英语？

那种方法不奏效的时候，他们有时会想到要寻求帮助。When that doesn't work they sometimes have the sense to seek help.国会有责任确保只有在所有和平手段都不奏效的情况下才会诉诸战争。Congress has a responsibility to ensure that all peaceful options are exhausted before resort ...