\(v = mx + C\)
\(v =\frac{1}{5} x +10\)
\(a =\frac{ vdv }{ dx }=\left(\frac{ x }{5}+10\right)\left(\frac{1}{5}\right)\)
\(a =\frac{ x }{25}+2 \Rightarrow Straight\) line till \(x =200\)
for \(x>200\)
\(v =\) constant
\(\Rightarrow a=0\)
Hence most approriate option will be \((a)\)