The correct answer is: C. Either I or II is implicit
The statement “With a sense of sincerity, quality teachers can improve the society” does not state that quality teachers are sincere, nor does it state that sincerity in teaching pays. However, it is possible that both of these statements are true. For example, if a teacher is sincere in their teaching, they are more likely to be effective in their job, which could lead to an improvement in the society as a whole. Additionally, if a teacher is seen as being sincere, they are more likely to be respected by their students and colleagues, which could also lead to an improvement in the society.
Therefore, either assumption I or assumption II could be implicit in the statement.