Final answer:
In chapter 6 of 'Animal Farm,' Squealer and Napoleon are able to trade with humans by using the windmill's profits.
Step-by-step explanation:
In chapter 6 of George Orwell's novel 'Animal Farm,' Squealer and Napoleon are able to begin trading with humans by using the windmill's profits (c)). The windmill, which the animals worked hard to build, generates income through the sale of surplus crops and electricity to other farmers in the area. This allows Squealer and Napoleon to engage in business transactions with humans, providing them with resources and goods that benefit the pigs' leadership.