Amit starts from a point a and walks to another points B, and then returns from B to A by his car and thus takes a total time of 6 hours and 45 minutes. If he had driven both ways in his car, he would have taken 2 hours less. How long would it take for him to walk both ways?

Let the time taken to walk one way be W and the time taken to drive one way be C. According to the first condition, walking one way and driving back takes 6 hours and 45 minutes. Equation 1: W plus C equals 6 hours 45 minutes. According to the second condition, driving both ways takes 2 hours less than the first scenario. Equation 2: C plus C equals 4 hours 45 minutes. From Equation 2, we find that driving one way (C) takes 2 hours and 22.5 minutes. Now, substitute the value of C back into Equation 1 to find the time taken to walk one way (W): W equals 6 hours 45 minutes minus 2 hours 22.5 minutes. W equals 4 hours 22.5 minutes. The question asks for the time taken to walk both ways (W plus W): 4 hours 22.5 minutes multiplied by 2 equals 8 hours 45 minutes. Therefore, the correct option is D.