In early February 2020, Wuhan City began to build three "( )" hospitals overnight to specifically treat mild pneumonia patients diagnosed with new coronavirus infection.

Answer: D

On February 3, 2020, Wuhan City began to build three "square cabin hospitals" overnight to specially treat confirmed patients with mild symptoms. In addition, there are 20 "makeshift hospitals" from all over the country rushing to assist Wuhan, treating cases for observation and diagnosis, treatment and testing of mild suspected cases. So the answer is D.