$10.(2$ points$)$ The MEL gene $($DNA$)$ is approximately $750,000$ base pairs $($bp$)$ in length. In skin cells, MEL mRNA is $40,000$ bp in length, whereas in eye cells the MEL mRNA is $80,000$ bp in length. Based on knowledge from this course, which of these could be responsible for these tissue$-$specific differences in mRNA length? o A poly$($A$)$ tail is added to MEL mRNA in skin cells but not in eye cells o MEL mRNA in skin cells has an additional stop codon o In skin cells, the $3$ end of MEL mRNA is degraded o MEL mRNA is alternatively spliced in skin cells compared to eye cells