A. During the 1960s and 1970s, the manufacturing industry was an important pillar of Hong Kong's economy. Since the 1980s, with the large-scale transfer of the original labor-intensive processing and manufacturing industry to the Pearl River Delta and other places, the status of Hong Kong's manufacturing industry has been declining, while the real estate, information, finance, tourism and other industries have been further strengthened. At present, the main industrial sectors are electronics, watches, clothing, plastics, toys, instruments, food and so on. So, A is wrong.

B, Hong Kong is a famous free port, and foreign trade has always been the leading industry in Hong Kong. So, B is wrong.

Hong Kong originally belonged to Xin 'an County, Guangdong Province (now Shenzhen), and was occupied by Britain after the Opium War. 1 July 19971day, China resumed the exercise of sovereignty over Hong Kong, established the Hong Kong Special Administrative Region, implemented "one country, two systems, and Hong Kong people ruled Hong Kong", and maintained the capitalist system in Hong Kong for 50 years.

D. Hong Kong is a famous free port, and foreign trade has always been the leading industry in Hong Kong. At present, Hong Kong is the eighth largest trade zone and an important entrepot for goods in the world. For more than half a century, Hong Kong has been a bridge between the mainland of China and the world. Therefore, d is correct.

Therefore, choose: d.