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

admin2009-05-28  28

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://jikaoti.com/ti/khPMFFFM
0

最新回复(0)