Answer:
Green truck.
Step-by-step explanation:
The gravitational force acting on any object is given as:
![f = m * g](https://img.qammunity.org/2020/formulas/physics/middle-school/xlbbinm4zcvw07xiz0h6wvt2c1d66dhlhb.png)
where, f = force due to gravity
m = mass of the object
g = acceleration due to gravity.
In the given option the mas of each box is same. Also all the trucks are identical. So the force will be more for the truck which has more no. of boxes loaded on it.
The green truck has 6 boxes and other trucks have less boxes. This is why the greatest force of gravity will be acting on Green truck.