An object starts to move in a straight line with constant acceleration A1 from its rest, and immediately changes to a straight line with constant deceleration A2 after time T1 When an object starts to make a uniform acceleration linear motion with acceleration A1 from its rest, and immediately changes to a uniform deceleration linear motion with acceleration A2 after time T1, and stops after time T2, the average speed of the object in all time is () A．a1 t1/2 B．a2 t2/2 C．（a1 t1+a2 t2）/2 D．

An object starts to move in a straight line with constant acceleration A1 from its rest, and immediately changes to a straight line with constant deceleration A2 after time T1 When an object starts to make a uniform acceleration linear motion with acceleration A1 from its rest, and immediately changes to a uniform deceleration linear motion with acceleration A2 after time T1, and stops after time T2, the average speed of the object in all time is () A．a1 t1/2 B．a2 t2/2 C．（a1 t1+a2 t2）/2 D．

You only offer three options
The maximum speed of the whole course is v = a1t1 = a2t2
Then the average velocity of the whole course is v / 2 = a1t1 / 2 = a2t2 / 2
A. B correct
C is wrong, (A1 T1 + A2 T2) / 2 = v