Answer:
d. inclusion of I1 in the mRNA
Explanation:
Introns are any nucleotide sequence within the gene that is non-coding and it is usually removed by RNA splicing.
When an RNA transcript is made, it is considered as pre-mRNA. The pre-RNA contains both the introns and the exons. For it to mature into mRNA, the introns should be spliced and the exons are joined together to form the mRNA.
A mutation might result to the intron I1 not getting spliced hence it will be included in the mRNA.