D. Governor Berkley's refusal to provide support against Native Americans.
Explanation:
The people were trying to expand their tobacco crop into Native American's "Sacred Ground" and when they ask Berkley for help he refused. This in time with the falling tobacco price (which was the reason they needed to expand the crop land) made once stable income farmers angry, leading to be one of the causations of Bacon's Rebellion.
Steps to get answer
I'm not going to lie I looked up "Why _(fill answer in here)_ was causing a problem for Bacon's people." But in all honesty why not use the largest resource the world has ever owned when it's in the palm of your hand. Otherwise I just recommend looking up the main subject of the topic followed by the question and you normally after a bit of research find your answer.