which of the following is the best answer to this question?

oneesanno tanjiyoubi wa itsudesuka?
1. aneno tanjiyoubi wa jiyuugonichi ichigatsu desu.
2. ane wa tanjiyoubi no jiyuugonichi ichigatsu desu.

The best answer to the question "oneesanno tanjiyoubi wa itsudesuka?" would be option 2: "ane wa tanjiyoubi no jiyuugonichi ichigatsu desu." This answer indicates that the older sister's birthday is on January 15th.