Which of this 2 affirmations is more close to the explanation of evolution?
The second is marginally better because it mentions randomness and emphasizes differential survivorship, but the parts about "trying to reach a target" and specifying a particular "task" are misleading at best. I would rewrite the statement as follows (I have edited for grammar, spelling and style as well, but emphasize more substantive deviations with strikeout for omitted parts and boldface for added parts). The substantive edits change the meaning of the statement significantly: most evolutionary biologists would be very uncomfortable with the second statement as written above (setting aside any grammatical issues).


  Evolution is has a random component but the species (or natural selection) tries to reach a target, may result in directional change: each generation has some random variation in traits but only individuals with beneficial traits tends to  are more likely to survive and produce offspring. For example, In order to survive the task is be 10cm taller. taller individuals survive better than smaller ones.  Some offspring are a half cm taller and other children are a half cm smaller; the latter die naturally and only the taller ones survive long enough to produce offspring.


I would probably say "offspring" rather than "children" in a technical context.

Note also that this emphasizes evolution by natural selection; broadly speaking, there are many non-adaptive processes (vicariance, drift ...) that also lead to evolution (change in gene frequencies between generations).