What's the meaning of dark matter?

Unseen matter that may make up more than ninety percent of the universe. As the name implies, dark matter does not interact with light or other electromagnetic radiation, so it cannot be seen directly, but it can be detected by measuring its gravitational effects.

Explanation:

Dark Matter is the theoretical matter that covers the ~85% of the universe. This matter is not visible to the eye or any scientific instrument (doesn't absorb or emit light). We can only observe dark matter by examining objects that have been "affected" by it.

Explanation:

i think its the first one

the correct answer is: b. pantala flavescens, because these organisms would have a high level of genetic variation due to sexual reproduction.  

because involves two organisms (parents) whose genetic material combines, sexual reproduction leads to genetic variation in new generations of offspring. the offspring is an unique organism, with new genome, more protected with the higher ability to adapted. this process is fundamental to evolution.