What does the term 'arduous' refer to?

The term 'arduous' describes a situation or task that requires a significant amount of effort, labor, and determination to accomplish, often due to its challenging nature. It captures the essence of difficulty and can be used to describe physical endeavors, such as climbing a mountain, as well as intellectual challenges, like completing a complex project. The connotation of the word suggests perseverance and hard work in the face of obstacles. This is why the definition aligns perfectly with the context of demanding great effort or labor, making it the appropriate choice.

The other options do not relate to the meaning of 'arduous.' For instance, having a natural tendency refers to an inclination, while extremely dry pertains to a lack of moisture. Ghost describes a supernatural entity, which is unrelated to the concept of effort or difficulty. Thus, the focus on effort and labor in the definition of 'arduous' is what makes it the correct answer.