The correct answer is B) external competition.
Although you forgot to include the map or the illustration, we did some deep research to help you and we can answer the following.
In the 17th and early 18th centuries, Britain's greatest challenge in controlling the North American Atlantic trade illustrated above was external competition.
On the map, we can see the Americas and the European continent with different trade routes across the Atlantic Ocean, and of course, Great Britain was not the only nation trading goods during the North American Atlantic trade. It was England, but also France, Spain, Portugal, Germany.
During the triangle trade years, African Slaves were sold to American landlords to put slaves to work for long hours in the farm fields to produce the kinds of crops that needed to be exported to Europe. European industries manufactured goods with those raw materials and sent them back to Africa and the Americas to be sold for good profits.
