Total change in momentum \(=\int F . d t=\) Area under Ft curve.
Area above \(t\)-axis will be positive and below \(t\)-axis will be negative in option \((c)\)
\(\text { Area }=-\left[\frac{1}{2} \times 5 \times 1\right]+\frac{1}{2} \times 5 \times 1=0\)