The correct answers that contributed to the heightened racial tensions during the 1906 Atlanta Race Massacre are:
B. Economic competition for jobs
C. The construction of a new city park
While other factors may have played a role in racial tensions in general, these specific issues were significant contributors in the context of the 1906 Atlanta Race Massacre. Option A regarding a disputed land ownership case may be relevant in some contexts but not specifically for the 1906 event, and option D is unlikely to have contributed positively to the situation.