$△ABC$中，$\angle B={120}^0$,$AC=7,AB=5$,则$\cos C=( \; )$

2016年天猫双11全天总交易额突破1207亿元，但在巨大的光环背后，也潜藏着虚假打折、质量低劣、售后服务缩水等方面的种种信任危机，成为网购业健康发展的重要障碍。为此国家应（    ）

①加快建立信用监督体系和失信惩戒制度             ②诚信经营，自觉维护消费者合法权益

③增强维权意识，提高辨别网购陷阱的能力         ④加快电子商务立法，完善对网店监管的法律监督体系

    My name is Dave. I have three good friends, Jack, Tom and Jim. Jack likes cakes, Tom likes fruit, Jim likes eggs and I like vegetables. We all like hamburgers. We eat hamburgers for lunch every day. Jack and Tom like French fries , and I also(也) like French fries, but Jim doesn't like them. For dinner, I don't like chicken,    ⑶    Jack, Tom and Jim like it. They all think chicken is very delicious.

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