MAS3:
The motor on the left can be driven to run both clockwise or counterclockwise.
You need to drive both wires to the motor, so you need two drivers.
The motors on the right can turn clockwise only.
Here you only need to drive one wire, the other can be fixed (to GND in this case).
So you can do with just one driver.
"So you can do with just one driver.", I don't understand, can I control the motors with just one driver?