第17题: [单项选择]Not until I reminded him for the third time ______ working and looked up. A. that he stopped B. does he stopped C. did he stop D. that he stop 参考答案:C 答案解析:[解析] nor until放在句首,句子要倒装。例如:Not until he finished his homework did Li Ming watch TV. (李明做完作业后才看电视。)
第18题: [单项选择]下列哪项病变不是维生素A缺乏的表现 A. 色盲症 B. 干眼病 C. 角膜溃疡 D. 角膜软化 E. 角膜穿孔 参考答案:A 答案解析:维生素A缺乏的最早症状是暗适应能力下降,严重时可致夜盲,即在暗光下视物不清。由于角膜结膜上皮组织、泪腺等退行性变,致角膜干燥、发炎、软化、溃疡、角质化等一系列变化,在球结膜出现泡状银灰色斑点。