Departments is the answer
I belive the answer to the first one is no I would have to assume a habitual zone is one area on a planet. for example, an air conditioned building vs. the Savvanah dessert. However I am not sure maybe other answers will help more on this one. Sorry.... Earth-like planet would of course need water, plant life, animals, oxygen, fossil fuels etc. A challenge we would face on a travel to another liveable planet: do we have engough transportation? engough fuel to make it? How long can we live on this planet? Who or what else is present here? etc. Yes I do think they should discover a planet with earth like qualities befor investing in tools to get us to them. So money is not wasted. (make sure to put this into your own words )
S.A Stands for Sine Anno.
Oxygen and glucose at top
carbon dioxide and water at bottom
