when top -down control occurs within an intertidal zone along the rocky coastline of the Pacific Ocean ,which of the following species controls the abundance of other species?

a_kelp
b)mussels
c)barnacles
d)starfish
My answer is b :)

No.

http://www.eoearth.org/view/article/156656/

To determine which species controls the abundance of other species within an intertidal zone along the rocky coastline of the Pacific Ocean, we can examine the concept of top-down control. Top-down control refers to the regulation of a population by predation or other factors at the top of the food chain. In this case, the species at the top of the food chain would have the ability to control the abundance of other species.

Among the options provided (kelp, mussels, barnacles, and starfish), the species that is typically considered a top predator in this ecosystem and has the ability to control the abundance of other species is the starfish (option d). Starfish are known to feed on a variety of intertidal organisms, including mussels, barnacles, and other invertebrates. By preying on these species, starfish can regulate their populations and exert top-down control.

Therefore, the correct answer is d) starfish.