The correct answer is C. the.
The Alps are a mountain range that runs through eight Alpine countries: Austria, France, Germany, Italy, Liechtenstein, Monaco, Slovenia, and Switzerland. They are the highest and most extensive mountain range system in Europe, forming a natural barrier between the northern and southern parts of the continent. The Alps are also one of the most popular tourist destinations in the world, attracting millions of visitors each year to enjoy their stunning scenery, winter sports, and summer hiking and biking.
The Alps are a relatively young mountain range, having formed about 30 million years ago as a result of the collision of the African and Eurasian tectonic plates. The mountains are still growing today, at a rate of about 1 millimeter per year.
The Alps are home to a wide variety of plant and animal life, including many species that are found nowhere else in the world. The mountains are also home to a number of important cultural and historical sites, such as the Matterhorn, Mont Blanc, and the Jungfrau.
The Alps are a truly unique and special place, and they are a source of great pride for the people who live in the Alpine countries.
The other options are incorrect because they are not definite articles. A definite article is used to refer to a specific person, place, thing, or idea. In this case, the Alps are a specific mountain range, so the definite article “the” is used.