Hey there!
Option D would be correct.
Hope this helps, tell me if I am wrong!
Introns because they are coding sequences.
Exons because they are non-coding sequences.
DNA ligase is the enzyme that repair irregularities and breaks in the back bone of double stranded DNA. The enzyme function by sealing the repair in the DNA, it seals recombination fragments and it connects okazaki fragments during replication of DNA.
If a mutation reduce the amount of ligase, all the functions of the ligase enzyme listed above will be affected negatively.
