The correct answer is - 1/5.
Even though Europe is a continent that is relatively small, in fact it is only the sixth largest, it still has approximately 1/5 of the total loess deposits on the planet. The reasons for this are simple, the relief of the continent and the rivers of the continent.
Almost all of Europe's loess deposits are located in the lowlands stretching from the northern part of France to the Ural Mountains in Russia, withe the southern part of England being i there as well. In this parts of the continent run most of the biggest rivers, the area is very low, the meandering of the rivers very high, and the floods from the rivers common in spring. All of the rivers come from the higher mountains, thus they bring in a lot of eroded material with them, which they deposit in the lowlands, thus making the continent very fertile in general.