The defect occurs in the first eight weeks of pregnancy, though no one understands why, said Dr. Solomon, the obstetrician with the Medical Center for Children, the University of Pennsylvania, Philadelphia, US.
【正确答案】 A
【答案解析】解析：defect“缺陷，毛病”；deficit“赤字，亏空(在医学上还有短缺之处的意思)”；deviation“派生，出处”；draw back“退缩”；discrepancy“矛盾，不符合之处”。根据句意，此处应是缺陷同义词，故选A。