spare no effort还是efforts

spare no effort 和 spare no efforts都是不遗余力的意思，但是根据前面的主语的单复数来决定后面的effort的单复数。例如：We should spare no efforts to further your interests。我们应该不遗余力的争取你的利益。I shall spare no effort to restore world trade by international economic readjustment, but the emergency at home cannot wait on that accomplishment。虽然我将不遗余力通过国际经济重新协调所来恢复国际贸易，但我认为国内的紧急情况无法等待这重新协调的完成。