If a big truck in front of your car begins to turn left, but its right turn signals are flashing, it is most likely that truck driver

a. started to turn left but forgot to turn off the right turn signals
b. is preparing for a u-turn
c. is preparing to turn right
d. none of the above

C. is preparing to turn right

Explanation:

A bigger vehicle requires large space to make a turn while moving in the road. Since the big truck cannot make a right turn instantly, otherwise the truck may tilt and roll. so the driver turn on the right turn signal to signal the traffic behind him that he is going to make a right turn and then begins to move left to cover a large space in order to make the right turn so that the truck does not roll.

So the answer is

C. is preparing to turn right