I’ll give you some key points and after that you should be fine, tide, swept underneath and over, density differences and climate change
        
             
        
        
        
Variations can be genetic or environmental, the traits are passed from one generation to other generation of snail is from from both parents to offspring and through the environment.
The correct answer is C.
Explanation:
Genetic variation in an organism is passed to the offspring by its parents.
environmental variation is the the result of different environment with which individual adapt.
Natural selection is a process in which a suitable trait which is well adapted to the environment is passed on tho future generations.
Genetic variation is the change in DNA or gene of the individual trait. The tree snails having different pattern in their shells is due to the habitat they are living in. 
The snails which have well adapted to the environment are able to reproduce and pass on the traits to their progeny. The variation is due to the traits passed from parents through the environment also.
 
        
             
        
        
        
The answer is A i just took the test
A- Mixture in which its components retain their identity.
        
             
        
        
        
<span>the branch of mechanics that deals with the mathematical
description of the motion and interaction of subatomic particles,
incorporating the concepts of quantization of energy, wave-particle
duality, the uncertainty principle, and the correspondence principle</span>