The correct answer is: C. opinion on
The preposition "on" is used to express an opinion about something. In this case, the speaker is expressing their opinion on the film, which is that it will win the national award.
The preposition "to" is used to express a purpose or destination. In this case, it would not make sense to say that the speaker's opinion is "to the film."
The preposition "about" is used to express a topic or subject. In this case, it would not make sense to say that the speaker's opinion is "about the film."
The preposition "for" is used to express support or approval. In this case, it would not make sense to say that the speaker's opinion is "for the film."
Here are some examples of how the preposition "on" is used to express an opinion:
- I have an opinion on the matter.
- What is your opinion on the new law?
- I'm not sure what my opinion is on that.
- I'm open to hearing your opinion on the matter.
- I'm not going to change my opinion on that.