Answer :
It's an arithmetic sequence. The first term is 1 and the common difference is 4.
[tex]a_1=1 \\ d=4 \\ \\ a_n=a_1+d(n-1) \\ a_n=1+4(n-1) \\ a_n=1+4n-4 \\ \boxed{a_n=4n-3} \\ \hbox{answer C}[/tex]
[tex]a_1=1 \\ d=4 \\ \\ a_n=a_1+d(n-1) \\ a_n=1+4(n-1) \\ a_n=1+4n-4 \\ \boxed{a_n=4n-3} \\ \hbox{answer C}[/tex]