Trademark infringement refers to the unauthorized use of a registered trademark by another person for commercial purposes without the permission of the trademark owner, or the use of a major part of another person's registered trademark as his own trademark, and used on the same or similar goods Generate trademark confusion to deceive consumers. According to the above definition, what is a trademark infringement in the following cases? ['An artist paints the trademarks of many big brands on one painting after artistic treatment, named "Modern".', 'After the "He Xiangu" trademark registered by company A was opened on the market, it was produced by the company B in the form of a branch factory with similar trademarks of "He Xiangu", and company A did not know.', 'Xiao Du named his study "Du Fu Thatched Cottage".', 'In order to highlight that their products are made of imported raw materials, the US flag is printed on the packaging.']