Why didn’t people begin to use unmanned vehicles in undersea exploration until recently? It is because of the ______. What

admin2014-10-11  62

问题 Why didn’t people begin to use unmanned vehicles in undersea exploration until recently?
   It is because of the ______.

What does the author mean by saying "more challenging" in the last paragraph?

选项

答案More demanding

解析
转载请注明原文地址:https://kaotiyun.com/show/05MK777K
0

最新回复(0)