Answer: Option A is not correct. In addition to porous and permeable rock,having at least one trap is important to the viability of the natural gas under the ground and prevents gas from flowing to the surface and spreading into the air. A trap is an impermeable layer on top of the formation rock that causes an accumulation of hydrocarbons such as oil and gas inside the reservoir rock. Option B is not correct either because there are other factors in addition to the amount and value of the gas,such as the depth of the reservoir rock, the type of layers to be drilled, etc. that are important to consider when deciding to drill a well. Option C is not correct since fine reservoir rock grains provide less porosity compared to coarse rock grains. In addition, rhombohedral packing provides less porosity compared to cubic packing.Option D is the correct option, as porosity is calculated as the ratio of pore volume to the total rock volume, which is equal to 20%.