If the same base pairs are used to code for all organisms, why is there so much variation among organisms?

A. The order of the codons differs between organisms.
B. The order of the codons is the same between organisms.
C. The codons in each organism are the same.
D. The codons in each organism differ.

Option A,  The order of the codons differs between organisms.

Explanation:

A codon is a group of three DNA or RNA nucleotide that encode for a particular protein. There are possibilities that diverse codon and their arrangements can code for a single protein. But in no case a single codon or codons arrangement can code for more than one protein. Then the question rises why variation is organism  arises if these set of codon is same in all. The answer to this question is varying sequence of the three codons among themselves. In totality there are 64 codons out of which 61 codon encodes for protein. Now these 61 codon can be arranged in unlimited  sets of three codon. This unlimited arrangement of codons bring changes/variation  in species.  

Hence, option A is correct

The order of the codons differs between organisms.

Explanation:

Genetic code may be defined as the triplet codon of the nucleotide that codes for the particular amino acids in the organisms. Hargobind Khurana gave important contribution in the genetic codes.

The genetic code is degenerative in nature means the single amino acids are coded by more than one codon. The arrangement of the codons determines the type of amino acids and these codons are universal in nature with few exception. The organisms show variation because order of the codon are different that read in the different fashions in the organisms.

Thus, the correct answer is option (A).

a physical change is being made.

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".