题目内容
A. system B. explorer C. invention D. mark E. man-made
1. to write or draw a symbol,line,etc. on sth. in order to give information about it
2. a thing that has been invented
3. made by people , not natural
4. a group of things that are connected or work together
5. a person who travels to unknown places in order to find out more about them
1.______ 2.______ 3._______
4.______ 5._______
l.D 2. C 3. E 4. A 5. B
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