The topic sentence, "Martin Luther King Jr.'s speech 'I have a Dream' has many brilliant examples of metaphorical language," is a subjective sentence.
In order to make it an objective sentence, you would need to remove the word brilliant (a). If you are objective about something it means you don't have any personal feelings towards it. Therefore, you are not stating that there are simply examples of metaphorical language, but don't have an opinion whether they are brilliant or not.
Nikita is the only witness to see you doing it but she made it up
To prove your innocence you would have to been with other people they would serve as witness saying you didn't do it even when you know you didn't in order to prove your innocence.
