Let's approach this multiple-choice question by a process of elimination. Option E is not the right answer, because Newton's mechanistic understanding of how the universe works had nothing to do with the spread of Enlightenment ideas, as a whole. Thinkers of the Enlightenment greatly admired Newton, it's true, but Newton himself was a deeply devout religious man whose entire worldview was radically at odds with philosophes such as Voltaire and Diderot.
The correspondence between the Royal Society and the American Philosophical Society undoubtedly facilitated the spread of Enlightenment ideas, to some extent, but both of these organizations were the preserve of an educational elite. Although literacy levels in the American colonies were high, a deep understanding of science and abstract political theory was not.
Option C can be discounted pretty quickly. George Whitefield was most certainly not an Enlightenment figure; quite the opposite, in fact. It's fair to say that Whitefield and the Great Awakening he inspired were not looked upon with any great sympathy by the likes of Benjamin Franklin or Thomas Jefferson.
Plantations may have been established to encourage European settlers, but, in actual fact, few made the journey. Plantation owners came to rely on slave labor from Africa and, naturally, this did nothing to facilitate the dissemination of Enlightenment ideals.
So that just leaves us with Option A. As mentioned earlier, literacy levels in colonial America were remarkably high. And even though most people wouldn't have been able to understand the latest proceedings of the American Philosophical Society, they did, nonetheless, have a firm grasp of the full important of Enlightenment ideas. They were able to do this because the key Enlightenment concept of government by reason, rather than authority, found practical expression in the intense political struggle between the American colonists and the British.