When an object moving in a straight line with uniform acceleration passes through points a, B and C in turn, the displacement XAB = XBC. It is known that the average velocity of the object in AB section is 3m / s, and that in BC section is 6m / s, then the instantaneous velocity of the object at point B is () A. 4 m/sB. 4.5 m/sC. 5 m/sD. 5.5 m/s

When an object moving in a straight line with uniform acceleration passes through points a, B and C in turn, the displacement XAB = XBC. It is known that the average velocity of the object in AB section is 3m / s, and that in BC section is 6m / s, then the instantaneous velocity of the object at point B is () A. 4 m/sB. 4.5 m/sC. 5 m/sD. 5.5 m/s

(1) According to the law of uniform acceleration linear motion, we can get: vb2-va2 = 2al2vc2-vb2 = 2al2va + VB2 = V1 = 3m / SVB + vc2 = V2 = 6m / s, we can get: VB = 5m / s, so we choose: C