Put the numbers in the data set in order from smallest to largest:
44, 45, 45, 47, 49, 50, 50, 51, 55, 55, 55, 56
The smallest number is 44, the largest is 56, so the outside lines need to be above those numbers.
Both A and B have that.
Now find the median ( the average of the middle two numbers)
The middle two numbers from the list are 50 and 50 so the median would be (50 +50) /2 = 100/2 = 50
The middle line inside the rectangle needs to be above 50.
This makes the answer A.