A delegation of some 150 Hong Kong youths, aged between 18 and 35, takes a group photo in front of a high-speed train at Shenzhen North Railway Station, June 26, 2018. They are on a five-day mainland summer trip, which began on Monday from Shenzhen. (PHOTO PROVIDED TO CHINA DAILY)

A senior train guard explains daily operation of China's extensive high-speed railway network to the Hong Kong youth delegation on a train from Shenzhen, June 26, 2018. (PHOTO PROVIDED TO CHINA DAILY)

Delegation members play a game during a journey by a high-speed train, June 26, 2018. (PHOTO PROVIDED TO CHINA DAILY)

Head of the delegation, Kenneth Fok Kai-kong, a Hong Kong member of the National Committee of the Chinese People's Political Consultative Conference, surprises a female member of the delegation with a birthday cake on the train, June 26, 2018. (PHOTO PROVIDED TO CHINA DAILY)

　　A sophomore from the City University of Hong Kong plays a game while on a high-speed train, June 26, 2018. (PHOTO PROVIDED TO CHINA DAILY)