What is sentence four referring to (“But when a long train of abuses…for their future security.”)?

the growing interconnectedness of the world through communication, trade, and the exchange of ideas is an important theme in the history of the 20th and 21st centuries.

explanation:

the industrial revolution pushed the world into modern industrialization. it changed the course of history profoundly. it caused rapid urbanization and pushed cities and countries into development. the industrial revolution began in great britain with a series with new inventions which led to the creation of machines and mass production.

this caused the country to gain wealth and money and become an international superpower. it improved transportation and manufacturing inside the country, pushed people to live in urban areas and britain to become the most powerful nation in the world for a while.