单选题 Be careful with those fireworks; they are ______ to go off unexpectedly.
A. available B. presumably C. easy D. able

【正确答案】 D
【答案解析】[解析] 考查知识点：be able to do的用法。该短语表示“能够做某事或者有可能做某事”。译文：当心那些烟花爆竹，它们会出人意料地爆炸。