Final answer:
A tongue flap significantly differentiates American and British pronunciation in words like 'cattle', 'city', and 'metal', where Americans might pronounce them as 'caddle', 'cidy', and 'medal'.
Step-by-step explanation:
The tongue flap, also known as a 'flapped T', creates significant differences between American and British pronunciations in words where an American speaker often flaps the T sound to sound like a quick 'D'.
An example of such words can be found in option c: cattle, city, metal, where an American might say 'caddle', 'cidy', and 'medal', respectively. The British pronunciation would maintain a clearer 'T' sound in these words. This difference arises due to variations in accent and pronunciation rules between American and British English.