Answer: If his plan is going to work.
Explanation: Clearly Jack is using STEM for his plan so making sure that his plan works could possibly be the answer. I mean if you were creating a project you would want to make sure that it works and that you checked your STEM skills to go forward with the plan.
I think it is D because in every paragraph you need 2 details about your topic
A great intellectual and cultural development in Europe and the United States is the source of many discoveries, inventions and revolutions, for example: Declaration of Independence of the USA or French Revolution. It's also the time of philosophers - like Montesquieu, Voltaire, Jean-Jacques Rousseau, Diderot or d'Alembert - who all focus on the same subject: the questioning of political structures and traditional value systems such as religion, absolute monarchy, education, science etc.
