In order for someone to shape steel into a sword’s blade, it is necessary to heat and cool the steel. This is often done using a large container of water. Assume a container of water is initially at room temperature (23°C) and the 7500 g steel blade of the sword is at 210°C. After the blade is placed into the water it comes to a final temperature of 25 °C. What is the approximate mass of the water?

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)