Answer:
The allusion in this case:
Kerry was doing pretty well on her diet, but the chocolate cake at the birthday party was her Achilles’ heel.
Is that Kerry's chocolate birthday cake was her weakness to break her diet.
Explanation:
Allusions are figures of speech that allow writers to express an idea with an indirect sentiment. In other words, they are tools that allow us to express an idea without calling it directly. The reason they are allusions is that they are taken from some popular or famous event, and we employ them to compare the situation or idea we want to express to that popular topic.
