Final answer:
The phrase 'My heart is racing 100 miles per hour' is an example of personification, attributing the action of racing to the heart.
Step-by-step explanation:
The phrase "My heart is racing 100 miles per hour" is an example of personification. Personification is a figure of speech where human qualities are given to animals, objects, or ideas. In the given idiom, the heart is described as if it could literally race like a car, which attributes the human action of racing to the non-human organ, the heart. It's an expressive way of conveying the feeling of a rapidly beating heart due to excitement, nervousness, or fear. This idiom is not an allusion, as it doesn't reference another work or historical event, nor is it alliteration, as it does not involve the repetition of initial consonant sounds. Additionally, similes are comparisons using 'like' or 'as', which is not the case in this idiom.