For this case we must find the unit cost of juice box of each option and compare:
Option A: 2 juice boxes for $ 0.66

Option B: 6 juice boxes for $ 1.92

Option C: 9 juice boxes for $ 2.97

Option D: 12 juice boxes for $ 4.20

The most feasible option is B. That is, buy 6 boxes for $1.92
Answer:
Option B