The answer is B. build up of plant materials. This is because those rocks that are composed of materials, which are organic matters from decaying plants, formed by biological activity are called biogenic or organic or non-clastic rocks. On the other hand, clastic rocks are made up of gravel, sand, silt, and clay.
It depends on the direction in which the shell is launched. The time can be anything from 3.6 seconds to never.
