The answer to your question would be the following one: In direct contrast. That is, your answer would be D.
Explanation:
By/in contrast is used when you are comparing two things or people and saying that the second one is very different from the first. In this case, the phrase is used to highlight the differences between the two proposals: the one by the teachers and the ones by the parents and the students. The second motion proposal is completely different from the first since it states that the school should start later the following year while the first one recommends to beggin earlier the current year.
