Okay, so the number of members gets added by 2 each month. In month 1, there are 8 members. It goes from 8 to 10 the second month, which means that in one month, 2 members joined. Now, in month 3, there are 14 students. That is adding 4 new students. Now, in month 4, there are 20 students. This is adding 6 new students. In month 5, there are 28 students, which means that you added 8 new students from last month.
So, you are basically taking the number of students added monthly, and adding 2 each time to the number of students added.
Month 6: 10 new students. So, there are 38 students in month 6.
Month 7: 12 new students. So, there are 50 students in month 7.
Month 8: 14 new students. So, there are 64 students in month 8.
Your answer is A) 64
~Hope I helped!~