Sedimentary Rock Help!?

It is a question of the energy of the environment of deposition. High energy environments have active currents and sediments that are in motion. A dead animal or plant under those conditions would most likely be destroyed. Of the choices listed, a conglomerate would represent such an environment. It is also important to note that there are fossils in that type of rock. The Petrified Forest of Arizona is within the Petrified Forest Member of the Chinle Formation and it is a conglomerate. So, if the remains are big enough and strong enough, they can survive even high energy environments.