The correct answer is doubts.
An illusion is a false perception of reality. It is a mental state that is not in accordance with the facts. A doubt is a feeling of uncertainty or lack of confidence. It is a state of mind in which one is not sure about something. A hallucination is a false perception of sensory experience that has no basis in reality. It is a mental state in which one sees, hears, or feels things that are not there. An imagination is a mental image or concept formed by the imagination. It is a state of mind in which one creates or forms mental images or concepts.
In the given sentence, the speaker is saying that they are confident in their abilities. They are not uncertain or unsure about their abilities. They are not seeing, hearing, or feeling things that are not there. They are not creating or forming mental images or concepts. Therefore, the correct answer is doubts.