Answer:
B) cos f
Explanation:
sin e = DF/EF
cos d = (which side is adjacent i don't even know)/EF
cos f = DF/EF
sin d = opposite (hypotenuse)/hypotenuse, doesn't make sense
sin f = DE/EF
life lesson in trig: don't try to do right triangle trig using the right angle, it won't work out