In a wild-type strain of Drosophilathe size of a gene from the start to stop codon is calculated to be 2000 nucleotide pairs. However, the size of the mRNA molecule transcribed from this gene is estimated at 1200 nucleotides. The most likely explanation for this discrepancy in size would invoke the existence of:
A)A new stop codon introduced by mutation
B)A frameshift mutation
C)mRNA degradation
D)DNA degradation
E)The presence of one or more introns

The correct answer is option E) "The presence of one or more introns".

Explanation:

Introns are non coding sequences located within genetic sequences that are removed during RNA maturation by a process known as RNA splicing. A gene that has 2000 nucleotide pairs but is translated into a mRNA molecule with 1200 nucleotides most likely have one or more introns that in conjunction are of 800 nucleotides in size. Once the intros are removed from the mRNA molecule the coding sequence is ready to be translated into a protein.

i would say it is

stimulus is a change in the environment that causes an organism to react. the response is the reaction to the stimulus. some examples of stimuli for zebras are drought, to many predators, and bad feeding grounds such as dead grass or plants. zebras respond to stimuli just like all other living organisms