There were 4 loaves of banana bread. 3/10 of each loaf was eaten. Thus, you can multiply 3/10 by 4 to find the total amount of banana bread remaining.
3/10 * 4/1 = 12/10
Simplify:
12/10 -> 6/5 -> 1 1/5
Thus D, 1 1/5 loaves remain at the end of the picnic.