Don’t listen to that link it’s a virus
Explanation:
The new research carried out by NASA on mars suggets that many of the Mars' ancient channel have been carved by flowing water, were actually formed by melt water beneath glacial ice sheets. The rocks looked familiar to the rocks found on Earth in these water channels. Moreover, conglomerate rock was found near the base of the channel on Mars.
I don't know exactly what you mean but the size of a group affects its defense because there is a larger group. Therefore, more people would be protecting it, adding more to its defense.
Wind energy
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