$x_1 = 1$

$x_{n+1} = x_n + 4$

The easiest way is to plugin $n = 1$ in the options (to get the 1st term): Only Option C gives the value as 1, which matches with the given value.

Answer C


Alternate:

$x_1 = 1$
$x_{n+1} = x_n + 4$

For $n = 1$: $x_{1+1} = x_1 + 4 => x_2 = 1 + 4 = 5$

For $n = 2$: $x_{2+1} = x_2 + 4 => x_3 = 5 + 4 = 9$

Thus, each term (from the 2nd term onward) is 4 more than the previous term; the series being: 1, 5, 9, 13, ...

It is clear that each term is 3 less than a multiple of 4 --- Option C