Answer: B.56
Explanation:
We know that to calculate the mean we need to add up all the observations, then divide by the number of observations .
The mean numbers of turkey vultures between March 10 and March 14 is given by :-

The mean numbers of great blue herons between March 10 and March 14 is given by :-

The difference between the mean numbers of turkey vultures and great blue herons observed at Hornsby Bend between March 10 and March 14=
.