Read the passage and discuss the questions onPage88. 1.How did the early explorers know where they were?They found out where they were by using stars. 2. What's the disadvantage of using the stars as guidingmarks? lts disadvantage is that it didn’'t work well when theweather was bad and the stars could not be seen.3.What is a GPS? Is it useful to use? lIt is like a man-made star. We can use it at any time, in anyplace and in any weather to find out our position. It is veryuseful. ·4. What do you think the GPS will be used for in the future?

根据首字母提示，完成短文。 Thanks to GPS, we can exactly know w here we arenow.GPS is like a man-made "star"'. It can be used inany place and any weather condition to find out ourposition. In the past, the early explorers had to usestars in the sky _to tell them where they were, however, this method didn't work well when the weather was bad.So GPS is a great invention that canhelp humans to better explore _our planets.