Which of the following is most likely to have the lowest porosity?

Granite is an igneous rock characterized by its interlocking crystal structure formed during the slow cooling of magma beneath the Earth's surface. This crystalline texture means that granite has very little to no pore space, resulting in low porosity. Porosity refers to the amount of void space within a rock that can potentially hold fluids. In contrast, sedimentary rocks like sandstone, conglomerate, and shale typically exhibit higher porosity as they often contain spaces between grains or layers that can contain fluids.

While sandstone may have high porosity due to its grain size and the arrangement of those grains, shale, despite being fine-grained, can also have some porosity, but it tends to be lower compared to sandstone. Conglomerate, with its rounded gravel and sand-sized particles, can have considerable porosity as well. Therefore, among the options given, granite stands out as having the lowest porosity due to its solid, dense structure and lack of voids.