The plus sign is used in addition and the minus is used in subtraction.加号用于加法;减号用于减法....using concrete objects to teach addition and subtraction.用实物来教加减法There will be simple tests in addition, subtraction, multiplication...
她患了夜盲症.She suffered from night blindness.他有夜盲症, 晚上看不见.He has night blindness , he is able to see nothing at night.这些医疗工作者会诊断出青光眼 、 夜盲症以及其他的眼部疾病.The workers look for conditions glaucoma, night blindness and other problems...