For a particle moving along x - axis, the acceleration a of the particle in terms of its x - coordinate x is given by a=−9x, where x is in meters and a is in m/s2. Take acceleration, velocity and displacement in positive x - direction as positive. The initial velocity of particle at x=0 is u=+6 m/s. The plot of velocity versus x - coordinate of particle in the duration it moves from origin towards the positive x - direction, is best represented by