ANSWER
B = {1, 2, 3, 4}
Step-by-step explanation
The symbol ⊆ means "contained" and this reads as "B is contained in A". If A is the set of all natural numbers, then set B must be a set of natural numbers. Remember that natural numbers are all the positive integers greater than 0, not including 0. From these options, the only set that has natural numbers is the third set: B = {1, 2, 3, 4}