人 民 网 版 权 所 有 ，未 经 书 面 授 权 禁 止 使 用
cmd: [Function: cmdValidatePromo], // The command waiting to be executed
。快连下载安装对此有专业解读
Automation: Rinsing It in Seconds
The “Knocking on Wood” Wikipedia page mentions Roud’s conclusion, and this claim of a 19th century origin has circulated online as the final say on the matter. If you go back to the original, though, Roud’s proposal actually ends on an ambivalent note: “Before this theory [of 19th century origins] can be finally accepted, however, an examination of the history of European forms of this custom would be advisable.”
This formula is satisfiable because if we set to b to true and a to false, then the whole formula is true. All other assignments make the formula false, but it doesn't change that the formula is satisfiable as long as there is at least one assignment makes the formula true.