The correct options are
C Maximum speed attained by the body between 0 to 4 sec is 4 m/s
D Particle retards for 2<t≤4
a=dvdt=2t−4
a<0 from 0 s to 2 s, therefore it is retarding
a>0 from 2 s to 4 s therefore it is accelerating
As it is retarding for the first 2 seconds, the minimum velocity occurs at t = 2 sec and it is equal to v(2)=22−4×2=−4m/s. Miniumum negative velocity means maximum speed.
∴ maximum speed is 4 m/s