题目内容：

阅读下面短文，按照句子结构的语法和上下文连贯的要求，在空白处填上一个适当的词，使短文通顺、意思完整。

    Some scientists believe that there will be more robots in 1. future. However, they agree it may 2. many years. These new 3. will have different shapes. Some will look like humans, and others might look like animals. In India, for example, scientists made robots that look like snakes. If buildings fall down with people inside, these snake robots can help look 4. people under the buildings. This was not possible 20 years ago, but computers and rockets also seemed impossible 100 years ago. We never know 5. will happen in 50 years.