Party B signs the contract, but Party A does not sign it. Whether the contract becomes effective depends on the situation.
 Only one party signs or seals the contract. If the other party performs the main obligations of the contract and is accepted by the other party, the contract is valid; If the above conditions are not met, the contract shall be invalid.
 [Legal Basis]
 In Article 490 of the Civil Code, if the parties conclude a contract in the form of a contract, the contract is formed when all the parties sign, seal or fingerprint. The contract is formed when one party has performed its main obligations and the other party has accepted them before signing, sealing or fingerprinting.
 A contract shall be concluded in writing as required by laws and administrative regulations or as agreed by the parties. A contract is formed when the parties fail to adopt a written form but one party has performed its main obligations and the other party has accepted it.