Since this is a timed test I'm pretty sure i'm too late to give the answer but it's C. Hope this helped (although i'm late)
Lincoln Issues the Emancipation Proclamation. One month later, after the qualified Union victory in the Battle of Antietam, Lincoln issued a preliminary proclamation warning that in all states still in rebellion on January 1, 1863, he would declare their slaves “then, thenceforward, and forever free.”
Answer:
Having a growth mindset (the belief that you are in control of your own ability, and can learn and improve) is the key to success. Yes, hard work, effort, and persistence are all important, but not as important as having that underlying belief that you are in control of your own destiny
