The correct option is D 37
First, note that each division on the Y- axis stands for 2 people.
Also, there are three bars before the month of October, with heights 12, 7 and 18.
These values represent the number of people who have their birthday in the months of January to September.
Therefore, the total number of people who have their birthday before October = 12 + 7 + 18 = 37.