The correct option is B −1 m2/s3
We know that acceleration from v−t graph is given by the slope of v−t graph
⟹a=dvdt=tan45∘=1 m/s2.
From v−t graph
At t=3 s, v=0
Using first equation of motion, we can say
v=u+at
⇒0=u+(1)(3)
∴ Initial velocity of the particle u=−3 m/s
At t=2 s
v=−3+1×2=1 m/s
∴v=−1 m/s
We know that, acceleration at t=2 s is a=1 m/s2
∴ Dot product of v and a at t=2 s is →v.→a=−1 m2/s3