The upside-down catfish is the only fish that _______ swims on i

The upside-down catfish is the only fish that _______ swims on its back.
A、habitually
B、traditionally
C、commonly
D、randomly
【正确答案】：A
【题目解析】：译文：反游鲶鱼是唯——种习惯上下倒着游动的鱼。A意为“习惯地，日常地”；B意为“传统地”；C意为“通常地，普通地"；D意为“随便地，无目的地”。根据句意知A对。答案为A。