Answer:
C. Varieties of an element that differ only in the number of neutrons are called isotopes.
Explanation:
The Earth is approximately 
old. The solar system formed from giant gas clouds which was a part of the solar nebula.
The surface of soil which demarcates two soils of different geological ages is called a unconformity.
Palesol is the soil that lies between sediments or volcanic deposits. If the paleosol is older they have lithified rock.
Hence, option C is true.
D. Introduce the bull again later I hope this helps!
Answer: achievement motivation.
Explanation:
Achievement motivation typically refers to the motivation if an individual to engaging in achievement. Achievement motivation is the need of a person to meet realistic goals, and be able to experience a sense of accomplishment.
Based on the information given, since we are informed that the more improvement Juan makes, the harder he practices. Therefore, the goal and the behavior by Juan illustrates achievement motivation.
