Look at the DNA sequence.

C G T T A C T G C A A T
G C A A T G A C G T T A
Which sequence shows a substitution mutation?

C G T T A C T G C A A T
G C A A T G A C G T T A

C G T A C T G C A A T
G C A T G A C G T T A

C G T C T A C T G C A A
G C A G A T G A C G T T

C G T G A C T G C A A T
G C A C T G A C G T T A

The sequence that shows a substitution mutation is:

C G T A C T G C A A T
G C A T G A C G T T A