参考答案：

The UN Convention on Contracts for the International Sale of Goods provides a number of rules that implement the seller’s obligations in respect of the quality of the goods. Article CE(A) states that, in general, the seller must deliver goods that are of the quantity, quality and description required by the contract and that are contained or packaged in the manner required by the contract. As regards quality specifically Article CE(B) provides that, except where the parties have agreed otherwise, the goods do not conform with the contract unless they: (a) are fit for the purposes for which goods of the same description would ordinarily be used. Goods are not fit under this case where they lack specific ordinary characteristics or when they have defects which impede their material use. Goods are also unfit for ordinary use when the defects, though not affecting the material use of the goods, considerably lessen their trade value; (b) are fit for any particular purpose expressly or impliedly made known to the seller at the time of the conclusion of the contract, except where circumstances show that the buyer did not rely, or that it was unreasonable for him to rely, on the seller’s skill and judgement. If the goods in question are to be used for other, non-ordinary purpose the buyer has no rights if he has not indicated the specific use; (c) possess the qualities of goods which the seller has held out to the buyer as a sample or model; (d) are contained or packaged in the manner usual for such goods or, where there is no such manner, in a manner adequate to preserve and protect the goods. Subparagraphs (a) to (d) apply whenever the parties have not agreed otherwise. If they are not to apply they must be expressly disclaimed in the contractual agreement. Article CE(C) goes on, however, to state that the seller is not liable under subparagraphs (a) to (d) above, if at the time of the conclusion of the contract the buyer knew or could not have been unaware of such lack of conformity. As regards liability, Article CF(A) provides that the seller remains liable for any lack of conformity which exists at the time when the risk passes to the buyer, even though the lack of conformity only comes to the attention of the purchaser after the risk has passed to them. Where the lack of conformity arises after the risk has passed to the buyer the seller remains liable if the lack of conformity arises as a result of a breach of any of the seller’s obligations, which include any guarantee that the goods will remain fit for their ordinary purpose, or for some particular purpose, or will retain specified qualities or characteristics for a period of time (Article (CF(B)). If the seller has delivered goods before the date for delivery, he may, up to that date, deliver any missing part or make up any deficiency in the quantity of the goods delivered, or deliver goods in replacement of any non-conforming goods delivered or remedy any lack of conformity in the goods delivered, provided that the exercise of this right does not cause the buyer unreasonable inconvenience or unreasonable expense. However, the buyer retains any right to claim damages (Article CG).