把带叶的枝条插到红墨水中，放到温暖有阳光的地方，等叶脉变得微红时，取出枝条，用清水冲洗干净，用刀片横切茎，看到许多红色小圆点，这些小圆点存在于（ ）
A．韧皮部
B．叶脉
C．形成层
D．木质部
答案：D
题目分析：树皮中含有韧皮纤维和筛管，筛管由上而下运输有机物；形成层的细胞能够不断的分裂向外产生韧皮部，向内产生木质部；木质部有木纤维和导管组成，导管自下而上运输水分和无机盐。故选：D．
| 阅读理解。 | ||||
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| 1. Where are Eric's dictionaries? | ||||
| A. On the bed. B. On the sofa. C. On the dresser. D. On the table. | ||||
| 2. ________ needs tapes. | ||||
| A. Eric B. Frank's uncle C. Mona D. Frank's mom | ||||
| 3. Are Mike's CDs on the table? | ||||
| A. Yes, it is. B. Yes, they are. C. No, they aren't. D. No, it isn't. | ||||
| 4. ________ are on the bed. | ||||
| A. Eric's math book and Mike's jacket B. Eric's math book and Frank's jacket C. Mona's math book and Mike's CDs D. Mike's jacket and Frank's tapes | ||||
| 5. Mike is Linda's _________. | ||||
| A. father B. uncle C. grandfather D. brother |