Me
what must occur to a shopping cart at rest in order to make it roll forward?
a) a force must be provided to overcome gravity.
b) balanced forces must be acting upon the cart.
c) an unbalanced force applied to the cart pushing or pulling it forward.
d) the unbalanced force acting upon it must be smaller than that of friction.

Because the sun is the biggest and if the sun orbits the earth we will be dead probably

The figure is missing but we can answer anyway.the correct answer is "releasing the string". in fact, when the person is holding the bow and the arrow, the kinetic energy of the arrow is still zero (because the arrow is not moving). the moment the arrow is released, it acquires a velocity v, so its kinetic energy will become different from zero: where m is the mass of the arrow and v its velocity.  all the other options, instead, do not increase the kinetic energy of the system: -  pulling farther back on the string : this will just increase the elastic potential energy of the system-  holding the arrow higher: this will increase the gravitational potential energy of the system (which is given by u=mgh, where h is the height above the ground)-  decreasing the mass of the arrow: this will decrease the gravitational potential energy of the system (which is given by u=mgh, where m is the mass)