To determine the size of the gorilla group after the changes, we can break it down step by step:
- Initial Group Size: 10 members
- Emigration: -4 females (10 - 4 = 6)
- Immigration: +2 females (6 + 2 = 8)
- Births: +2 gorillas (8 + 2 = 10)
- Death: -1 male (10 - 1 = 9)
After accounting for all these changes, the final size of the group is 9 members.
So, the correct response is 9.