Answer:
every group of her community
Explanation:
To get an appropriate sample for her survey, she needs to survey people from various groups of the community.
If she surveys only dog owners, even only pet owners, chances are most people in that group would be in favor of the park, biased sample.
If she surveys only non-pet owners, the results will most likely show a minority of support.
The pet owners (or just dog owners) should be surveyed in a relative proportion of the general population of the community, so their opinion is neither over-weighted nor under-weighted in the results.