根部的根毛吸收水分以后，把水分运输到茎、叶上去的是根部的（ ）
A．伸长区细胞
B．成熟区细胞
C．成熟区导管
D．成熟区根毛
根尖是指从根的顶端到生有根毛的一段．它的结构从顶端依次是根冠、分生区、伸长区、成熟区．如图：
根冠位于根的顶端，属于保护组织，细胞比较大，排列不够整齐，像一顶帽子似地套在外面，具有保护作用．
分生区被根冠包围着，属于分生组织，细胞很小，细胞壁薄，细胞核大，细胞质浓，具有很强的分裂能力，能够不断分裂产生新细胞，向下补充根冠，向上转化为伸长区．
伸长区在分生区上部，细胞逐渐停止分裂，开始迅速伸长，是根伸长最快的地方，是根深入土层的主要推动力，能够吸收水分和无机盐．
成熟区也叫根毛区，在伸长区的上部，细胞停止伸长，并且开始分化，表皮细胞的一部分向外突起形成根毛，是根吸收水分和无机盐的主要部位．成熟区及其上部，根内部一部分细胞分化形成导管，能输导水分和无机盐．
因此把水分运输到茎、叶上去的是根部的成熟区导管．
故选：C
Job stress has been known to cause heart problems in people who already have cardiovascular(心血管) disease. Now Finnish scientists have shown that 50 in healthy people the pressure of work can cause damage. High blood pressure, lack of 51 , smoking and being overweight 52 to heart disease—a 53 killer in many industrialized countries. But Mika Kivimaki, of the Finnish Institute of Occupational Health, and his colleagues, who studied the 54 histories of 812 healthy Finnish men and women in a metal industry company over 25 years, said job stress also plays an important role. Workers who had the highest job-related stress levels at the start of the study were more than twice as 55 to die of heart disease, 56 the study published in The British Medical Journal. Work stress 57 too much work as well as a lack of satisfaction and feeling undervalued and 58 . Many people work long hours but if the effort is 59 the stress is minimized. Kivimaki said job pressure is damaging when being overworked is 60 with little or no control, unfair supervision and few career opportunities. The British Heart Foundation said the results 61 earlier research showing that people in jobs with low control, such as manual workers, could be at greater 62 of heart disease than other employees. “It is 63 for people to try to minimize levels of stress at work and for employers to 64 people to have more control at work and to be rewarded for their success,” the foundation said in a statement.
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