Igneous rocks form from the cooling and solidification of lava or magma.
I'm not a big fan of this question, but I think the "desired" answer is grain-size (from very large to microcrystalline) and interlocking texture.
(It could be tendentiously argued that tuff (also called tufa) and possibly other pyroclastic rocks, which form from volcanic ejecta, lack an interlocking texture because they are more like sediments that are welded together. I say this is tendentious because such rocks are about as much sedimentary as they are igneous, and are not typical igneous rocks if they are igneous rocks at all.)
The correct answer is - Eiffel.
Vulkaneifel (Volcanic Eifel) is a remnant of the volcanic past in the Eifel Mountains Range in Germany. It is very easy easy to see that this region has been shaped by volcanic activities in the past because it has lots of typically volcanic landmarks, like lava streams, craters, tuffs. This region is located between the Rhine and Wittlich Depression, and is divided into three parts, Volcanic West Eifel, Volcanic High Eifel, and Volcanic East Eifel.
Volcanic soil has a lot of minerals that plants take in as nutrients.
The correct answer is - A. each nation desires an independent sovereign state.
It is very rare that a multinational state can function without any ethic or separatist problems. Most of the ethnic groups want to have their own independent state and not be ruled by someone else from another ethnic background. There lots of examples of this throughout the world, like Spain, were the Catalans in the northeastern part of the country, and the Basques in the northern part of the country, have strong separatist movements, and have been trying for decades to become independent states.