Total distance covered by car =35+69

    =104 km/hr

Total time of the journey=45+75= 120minutes

= 2hr

Average speed of the car =$\frac{\mathrm{total} \mathrm{distance}}{\mathrm{total} \mathrm{time}}$

     =$\frac{104}{2}=52$ km/hr

Hence, Option C is correct.