题目

用显微镜观察根尖的永久纵切片时，视野中的细胞很小，排列紧密，细胞壁薄，细胞核大，细胞质浓。此部位属于（ ）。 A.根冠   B.分生区  C.伸长区  D.成熟区 答案：BTraffic restrictions have come into effect in Beijing      to improve thecapital’s air quality and traffic situation for the 2008 Olympics．A．in order thatB．in an attemptC．at an attemptD．in a try