Answer:
Option C.
Scientist explain the incomplete fossil record because not all organisms become fossils. Processes like erosion and mountain building can change rock layers, causing fossils to be spread over multiple layers or destroyed.
Explanation:
- Fossils are the remains of organisms that are found on the rocks after they die.
- So, no one can be 100% sure about the complete fossil record because of the continuous process like erosion and other natural calamities.
- The sediment must cover any organism's remains to start the fossilization process to start. Most of the organisms start decomposing  before this process can be executed.
 
        
             
        
        
        
The answer to your question is B- introduction of non-native animal species 
        
                    
             
        
        
        
Answer:
1. gravel of the sand: a part is dissolved and the remainder is grouped at the bottom of the beaker.
2. drop of sunflower oil: It is not absorbed and heaps on the surface of the water contained in the beaker.
Explanation:
Gravel of the sand is a polar substance. This means that this substance has the ability to dissolve and mix with water in a system in which both were placed together, such as a beaker, for example. However, the beaker limits the amount of water, which limits its ability to dissolve polar substances. Therefore, depending on the quantity, the gravel of the sand, when placed in a beaker with water, will dissolve, in parts, what is not dissolved will accumulate in the bottom of the beacker, because the gravel of the sand is denser than the water.
With the drop of sunflower oil the exact opposite happens. This is because drops of oil are nonpolar substances, which means that they do not have the ability to be dissolved in water. This means that when dropped into the beaker with water, the drop of sunflower oil will not dissolve, but will pile up on the water surface, because it is less dense than water.