1 is CORRECT. Plotting F=SUM m(1,3,11,12) on a K-map would result in 1-entries in cells 1,3,11 and 12, which is what you want. Note that for a 4 variable K-map the labels dictate the following order for the minterm cells:
0 4 12 8 1 5 13 9 3 7 15 11 2 6 14 10