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

admin2009-05-28  30

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

Why is ocean exploration not so expensive as space travel?
Because ______ for submersibles to get away from the Earth’s gravity.

选项

答案there’s no need

解析
转载请注明原文地址:https://jikaoti.com/ti/rhPMFFFM
0

最新回复(0)