Heightened racial tensions can often stem from a variety of social, economic, and political factors. In the context you've provided, the following contributing factors are likely relevant:
A. Disputed land ownership case - Disputes over land ownership can exacerbate racial tensions, especially if the case involves historic injustices, discrimination, or claims to land by marginalized communities.
B. Economic competition for jobs - Economic competition, especially in contexts where jobs are limited, can lead to tensions between different racial or ethnic groups, particularly if there is a perception that one group is favored over another.
C. The construction of a new city park - While a new city park can be seen as a positive development, if the construction process involved the displacement of communities or did not include input from diverse community members, it could lead to racial tensions.
D. Celebrations of cultural diversity in the city - Although this might be seen as a positive aspect of community relations, if not handled inclusively, or if certain groups feel excluded from the celebrations, it could lead to tensions.
In summary, both the disputed land ownership case (A) and economic competition for jobs (B) are strong factors that can contribute to heightened racial tensions. The other options could also contribute under certain circumstances, but the first two are more directly linked to conflict.