Change to the landscape from construction. The answer is c because if there is construction, they are probably building something on top of what used to be that ecosystem.
The answer here is D, and it's kind of obvious. But you probably already knew the answer and are just doing this for piece of mind.
Explanation: Just the fact that we don't know whether or not there even is extraterrestrial life rules out every other answer, without even needing to go in depth.
(Okay, I read your question completely wrong, it's asking for which one of these has been solved isn't it?)
This is tough because all of these other than D have been figured out. Go with the methane atmosphere then.
Surface tension in water owes to the fact that water molecules attract one another, as each molecule forms a bond with the ones in its vicinity. ... This inward net force causes the molecules on the surface to contract and to resist being stretched or broken.
