Snellen视力表的标准测试距离为
3.Now read the following sentences. Check True (T), False (F), or Not Mentioned (NM) in the box given below.The two sisters see each other almost every day.( )
sdf sdf
SD卡和CF卡的插拔方法是一样的
SD法是1957年美国心理学家奥斯古德提出的