Question

Two species have a relationship with one another in an ecosystem. Suppose one of these two species goes extinct. Which type of relationship did the two have if the surviving species population increases after the other goes extinct?
A. THe extinct species was a parasite in a parasitic relationship with the surviving species.
B. The extinct species relied on the surviving species in a commensal relationship.
C. The two species had a mutualistic relationship.
D. The surviving species preyed on the extinct species.
Please help me! I think the answer is A but I am not sure if I am correct.