Which one of the following interspecies relationships has a negative effect on the abundance of both species?
a. commensalism
b. parasitism
c. predation
d. competition
(i know that b is wrong)

D. Competition. Competition is a negative type of interaction among organism of the same (intraspecific) and different (interspecific) species. Organisms often compete when there is less resources in the environment. Because other organisms may be consuming or defending a resource, other organisms that need it need to compete, thus reducing the growth and survival of both competing organisms.

Wetlands form where water and land meet. a lake with a wetland fringe can fill in with decayed plant and animal material to become a wet meadow. a pond can fill in to become a bog or fen. sediment can fill in a river marsh to become a swamp.flooding of coastal lowlands from rising sea levels has created broad coastal marshes that are protected from wave action by barrier islands or reefs. coastal wetlands also form when rivers deposit sediment as they reach the ocean. plants then take root and hold the soil firm against the forces of tides and waves.