The scientists have made an ________ study of the viruses that cause the disease.
句意：科学家们对引起这种疾病的病毒进行了详尽的研究。exhaustive详尽的；彻底的。 exhausted疲惫的；耗尽的。exhausting使筋疲力尽的；使耗尽的。exhaustion枯竭；耗尽。故选C。