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...