The answer to the question is the letter D.
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Answer:
C
Explanation:
Since air molecules (the particles of the medium) are moving in a direction that is parallel to the direction that the wave moves, the sound wave is referred to as a longitudinal wave. The result of such longitudinal vibrations is the creation of compressions and rarefactions within the air.
Hope This Helped, -James
The Balkan range runs 560 km from the Vrashka Chuka Peak on the border between Bulgaria and Serbia eastward through central Bulgaria to Cape Emine on the Black Sea. The highest peaks of the Balkan Mountains are in central Bulgaria. The highest peak is Botev at 2,376 m, which makes the mountain range the third highest in the country, after Rila and Pirin. The mountains are the source of the name of the Balkan Peninsula.
The mountain range forms the watershed between the Black Sea and Aegean Sea catchment areas, with the exception of an area in west, where it is crossed by the spectacular Iskar Gorge. The karst relief determines the large number of caves, including Magura, featuring the most important and extended European post-Palaeolithic cave painting, Ledenika, Saeva dupka, Bacho Kiro, etc. The most notable rock formation are the Belogradchik Rocks in the west.
There are several important protected areas: Central Balkan National Park, Vrachanski Balkan Nature Park, Bulgarka Nature Park and Sinite Kamani Nature Park, as well as a number of nature reserves. The Balkan Mountains are remarkable for their flora and fauna. Edelweiss grows there in the region of Kozyata stena. Some of the most striking landscapes are included in the Central Balkan National Park with steep cliffs, the highest waterfalls in the Balkan Peninsula and lush vegetation. There are a number of important nature reserves such as Chuprene, Kozyata stena and others. Most of Europe's large mammals inhabit the area including the brown bear, wolf, boar, chamois and deer.
The Balkan Mountains played an enormous role in the history of Bulgaria since its foundation in 681 AD, and in the development of the Bulgarian nation and people.
The correct answer is - d. Humans changed from a hunter-gatherer society to settling in farming villages.
With the domestication of animals humans didn't really had that much of a need to hunt animals, because the animals were now in their villages and were controlled by them. Humans chose carefully which animals to domesticate according to their usefulness, so they started domesticating animals that were able to provide meat, eggs, wool, milk, working/transportation force. This enable the humans to have a much more stable food source and also to not be in constant risk of getting an injury or even be killed during a hunt.