Once upon a time， there lived a teacher In a small town. He often taught his students in special ways. Once he Rent four of his students to go to a small farm to see apple trees in different seasons. The first student went in winter， the second in spring. The third in summer. And the last in autumn.

    After the four students came back .the teacher called them together. They pictured (描述) their feeling to the teacher. The first student said that there were no leaves on the trees. It made him very disappointed. The second student said his eyes were full of light green. It made him feel hopeful. The third one disagreed. ”What are you talking about? How pretty the trees were! The sweet smell of the beautiful flowers spread (传播） here and there.” The last one shook his head. He only saw a lot of apples on the beautiful trees.

    The teacher smiled and told his students none of them were wrong. They each just saw one season. He continued， “The trees are not the same in different seasons. You can't judge (判断)a tree by only one season. Don' t let the regret of one season destroy the beauty of the rest. '

    Everything has different sides in our life. Don't hurry to make a conclusion(结论)before seeing the whole of it.

舱外航天服实际上是最小的载人航天器，是航天员走出航天器到舱外作业时必须穿戴的防护装备如图27所示．舱外航天服质量仅约110kg，除了具有舱内航天服所有的功能外，还增加了防辐射、隔热、防微陨石、防紫外线等功能．舱外航天服主要由外套、气密限制层、液冷通风服、头盔、手套、靴子和背包装置等组成，是一种多层次、多功能的个人防护装备．气密限制层是舱外航天服最重要的部分，它的作用是保持服装气密，限制服装膨胀，使各大关节具有一定的活动度．液冷通风服穿在气密限制层内，在服装的躯干和四肢部位有网状分布的塑料细管，液体流过时可将热量带走．