Cao Cao, also known as King Wei Wu, was excavated in the tomb of Xigao cave in Anyang, Henan, with grave engraved with "Weiwu King Gehu Euphorbia" and a stone pillow with "Weiwu commonly used Wei Xiang stone". If one of the following is true, the above inference can be best strengthened. ['Funeral objects are important evidence to prove the identity of the tomb owner.', 'If no grave engraved with the words "King Wei Wu" is found in the tomb, it cannot be proved that the tomb is Cao Cao\'s tomb.', 'The grave was found to be Cao Cao\'s tomb only if a funerary engraved with the words "King Wei Wu" was found in the tomb.', 'As long as a funerary inscribed with the words "King Wei Wu" is found in the tomb, the tomb is Cao Cao\'s tomb.']