The correct answer is C. 224
Further details:
Using the formula for calculating the sum of an arithmetic sequence
[tex]S_{n} = \frac{n}{2} (2*a_{1} +d(n-1)) \\ S_{7} = \frac{7}{2} (2*17+5(7-1)) \\ S_{7}=\frac{7}{2} (34+30) \\ S_{7}=\frac{7}{2} (64) \\ S_{7}=\frac{7*64}{2} \\ S_{7}=\frac{7*32}{1} \\
S_{7}=224[/tex]
