Conclusion-I: This conclusion follows logically. From the statements, we know that some doctors are teachers, all teachers are engineers, and all engineers are scientists. This creates a chain: Since some doctors are teachers, those doctors are also engineers (Statement-2). Since all engineers are scientists, these doctors who are engineers are also scientists. Therefore, some scientists are doctors.

Conclusion-II: This conclusion does not follow. Statement-2 only states that all teachers are engineers, but it does not imply that all engineers are doctors. There could be engineers who are not doctors.

Conclusion-III: This conclusion follows. Since some doctors are teachers and all teachers are engineers, it follows that some engineers are doctors (those engineers who are teachers and also doctors).