The ability of carbon to form long chains is called Catenation.
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.
Obviously larger than normal meals may lead you to gain weight.
Industrial melanism is an evolutionary effect prominent in several arthropods, where dark pigmentation has evolved in a habitat affected by industrial pollution, including sulphur dioxide gas and dark soot deposits.
C.stressors are activities that can cause danger
