下列有关生物圈的描述中，不正确的是（ ）
A．生物圈是最大的生态系统
B．地球就是生物圈，到处都有生物生存
C．生物圈中多种多样的生态系统都不是各自独立的，而是相互都有联系的
D．生物圈为生物生存提供了基本条件：阳光、空气、水、适宜的温度、营养物质、一定生存空间，生物圈是所有生物的家
生物圈是地球上的所有生物与其生存的环境形成的一个统一整体，生物圈的范围：以海平面为标准来划分，生物圈向上可到达约10千米的高度，向下可深入10千米左右深处，厚度为20千米左右的圈层，包括大气圈的底部、水圈的大部和岩石圈的表面，生物圈为生物生存提供了基本条件：阳光、空气、水、适宜的温度、营养物质、一定生存空间，生物圈是所有生物的家，生物圈包括所有的生态系统，是最大的生态系统，生物圈中多种多样的生态系统都不是各自独立的，而是相互都有联系的．
故选：B
1. Decide which is closest in meaning to the underlined word "stiff" in the text.
A. Unable to bend
B. Dry, loose and smaller
C. Not easy to turn or move
D. Less straight as well as narrow
2. "And she needed to be lucky ."What did this sentences suggest?
A. God would bring luck to her.
B. Good luck was sure to reach her.
C. She needed to try hard to be lucky.
D. There was a chance that her efforts would end in failure.
3. From the text, we learn that Houston was probably the name of ________.
A. the operation room
B. the most unusual surgery
C. a city where the hospital lay
D. the head doctor in charge of the operation
4. From the text, we can tell that________.
A. the Davids got along well with each other
B. David accepted Flora's advice without any hesitation
C. David's father died from a sudden attack of heart trouble
D. David became a normal person soon after the medical operation