The correct option is D first decreases and then increases
From t=0 sec to t=t0 sec
The slope of the graph is positive(i.e.dvdt=+ve) so, acceleration is positive and velocity is negative in this time interval.
Therefore, the speed of the particle will decrease first.
After t=t0 sec both acceleration as well as velocity are positive so, the speed will increase after t=t0 sec.
Hence speed of the particle will decrease first and then increases.