Answer: 1. Suggests.
Step-by-step explanation: The tone of a text or sentence is the author's or speaker's attitude towards the audience, the subject or even the characters of the text. There are many different kinds of tones, like: positive, negative, objective, sad, angry, etc. The given phrase is an example of a sentence with a subjective tone, because it is influenced by the writer's opinion, to create an objective tone, we should replace the phrase "indisputably proves" with the word "suggests" because it is a more neutral expression.