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.
Answer:
In World War I, hand grenades were also known as “hand bombs.” The general philosophy for their use in the fighting armies was that grenades could kill the enemy underground or behind cover. ... Offensive grenades used concussion, or shock-waves, to wound, while defensive grenades exploded, scattering shell fragments.
Explanation:
<span>A Century of Dishonor. Injustices to the Native Americans in the United States. A Century of Dishonor is a non-fiction book by Helen Hunt Jackson first published in 1881 that chronicled the experiences of Native Americans in the United States, focusing on injustices.</span>
Answer:
Dr. Ingram conducted an C. experimental study.
Explanation:
An experimental study is that in which the variables are in direct control of the researcher. He/she is in control of <em>changing or adjusting</em> them in order to reach an outcome.
Dr. Ingram <em>varied the imageability of items </em>on a list to measure the participants' recalling abilities. He is conducting an experimental study.
Let's see why the other options are not valid in this case:
- A correlational study tries to find correlations between 2 or more variables.
- In a naturalistic study the researcher observes a certain phenomenon.
- An observational study just centers on observing, there is no manipulation of variables.
