Final answer:
The language device in the phrase is Parallel Structure, which uses repetitive patterns to highlight the importance of ideas.
Step-by-step explanation:
The language device used in the phrase "a single story of Africa: a single story of catastrophe" is C. Parallel Structure. Parallel structure involves the repetition of the same pattern of words to show that two or more ideas have the same level of importance.
In the given phrase, the repetition of the words "a single story of" before introducing each idea emphasizes the notion that there is a monolithic perception being described, thus making the statement more impactful and memorable.