A) <u>Mutation</u> is the original source of variations for plants and other organisms  which develops differences among their respective species
Explanation:
Genetic variation leads to the natural differences between each individual and among individuals of a species. The main cause for this variation is due to alleles that cause variations in the composition of genes or the DNA sequences.  
A mutation is a genetic variation which leads to the creation of a new allele in a species population. Each variation in the DNA sequence leads to an allele formation and each allele leads to a difference in character or trait between individuals since they are the alternate version of the original genes.  
Although genetic variations could be brought about by crossing over, random fertilization, or independent assortment; mutation is the original source because it provides the basic raw material for all the evolutionary changes.
 
        
             
        
        
        
Explanation:
cloth is a insulator so it stops heat from passing 
 
        
             
        
        
        
Carbon is an element 
Oxygen is an element
        
                    
             
        
        
        
No generations or hybrid would form before meselson and stahl would have observed evidence of a band in the cscl gradient.
The conservative model predicts that, following a single replication, half of the newly formed DNA double helices will be made entirely of the original, or old, DNA, and the other half will be entirely new. Then, each double helix would be completely replicated during the second round of replication. After that, 25% of the double helices would be all new, and 25% would be entirely old. Thus, the fraction of entirely new DNA double helices would increase with each succeeding round of replication, but the total number of completely unique DNA double helices would remain constant. Therefore, no hybrid DNA molecule containing 14N and 15N is replicated in the conservative model.
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Answer:
D)  Can simple organic molecules form spontaneously in an oxygen-free atmosphere?
Explanation: