Question

which example best illustrates the process of natural selection?
giraffes with short necks migrated to locations best suited for their neck lengths.
giraffes stretched their necks to reach for food and the resulting offspring had longer necks.
giraffe necks varied in length and the giraffes with short necks were at a disadvantage.
giraffe necks varied in length and all offspring had an equal chance of survival.

Explanation:

Natural selection is the process where organisms with favorable traits are more likely to survive and reproduce. In the case of giraffes, if neck lengths vary and short - necked giraffes are at a disadvantage (e.g., can't reach food as well), this shows natural selection. Migration (first option) is a different process. The second option is Lamarckian (acquired traits being passed on, which is not how natural selection works). If all offspring have equal survival (fourth option), there is no selection pressure.

Answer:

Giraffe necks varied in length and the giraffes with short necks were at a disadvantage.