【正确答案】 D

【答案解析】原文：According to China Daily, the so-called “996” work schedule, in which employees work from 9 am to 9 pm, six days a week, spread from IT to other industries. Some companies may even demand more overtime. In a 2018 study, more than 80 percent of Chinese employees said they were overworked and under mental and physical stress. This can cause depression, weight gain and sleep deprivation, which lower work productivity.根据新闻定位句可知，美国东南部克林奇河的贝类贻贝大规模死亡可能是一种传染性疾病引起的。故选D。