如图所示，将凸透镜看作是眼睛的晶状体，光屏看作是眼睛的视网膜，烛焰看作是被眼睛观察的物体．拿一个近视眼镜给“眼睛”戴上，光屏上出现烛焰清晰的像，而拿走近视眼镜则烛焰的像变得模糊．在拿走近视眼镜后，为了能在光屏上重新得到清晰的像，下列操作可行的是（　　）

根据短文内容，选择正确答案。

    The computers changed our lives in the 1980s, the Internet changed our lives in the 1990s, and the robots will change our lives in the new century.

    Do you think there will be robots in people's homes? It's not a dream that every home will have a robot.

    Now, robots are not only able to help people do the housework, they can also help the doctors do the difficult operations, play chess with people, play the piano and so on.

    A new cooking robot is used in Beijing. It can cook all the dishes on the menu; you only need to wait two to four minutes. In the future, the robot will be a nurse, a security (安全）guard, or a partner in your life.

    Experts believe robots will be used everywhere from the industrial (工业的） robots to service robots. In the future, robots will become part of the family, and provide close service for people. We all look forward to the new robot age.

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．

20世纪80年代，下列国家中国民生产总值跃居世界第二位，仅次于美国的是（    ）