Explanation:

- Avi can complete the project in 4 hours, which means he completes 1/4 of the project in one hour.

- Bindu can complete the project in 12 hours, which means she completes 1/12 of the project in one hour.

- They work alternately, starting with Avi. So from 5 a.m. to 6 a.m., Avi works, completing 1/4 of the project.

- From 6 a.m. to 7 a.m., Bindu works, completing 1/12 of the project.

- After 2 hours, they have completed (1/4 + 1/12) = 1/3 of the project.

- They continue this pattern. By 9 a.m., Avi works for 3 hours total, completing 3/4, and Bindu works for 2 hours, completing 1/6.

- By 10 a.m., they would have completed (3/4 + 1/6) = 11/12 of the project.

- Avi works again from 10 to 11 a.m. and completes 1/4 more, finishing the project.

- 11 a.m. is the correct answer.