The sugar dissolved in water gradually; finally all that remained was an almost______residue on the bottom of the glass.
【正确答案】 B
【答案解析】解析：fragrant“芬芳的”；imperceptible“无法察觉的”；glassy“像玻璃的”；opaque“不透明的”。根据题意，糖放入水中，就会慢慢溶化，直至水糖一体，几乎看不出任何糖的痕迹。故选B。