Correct Answer - B
Till 11s, acceleration is positive, so velocity will go on increaseing up to 11 s and maximum velocity will happened at 11s. The area under the acceleration -time graph gives change in velocity. Since particle starts with `u = 0`, change in velocity is
`v_(f) - v_(i) = v_("max") - 0 =` Area under `a - t` graph
or `v_("max") = (1)/(2) xx 10 xx 11 = 55 ms^(-1)`