2. which metal ion produces the light with the highest energy?
na+
ca+
k+
ba2+

"K+" is the one metal ion among the choices given in the question that produces the light with the highest energy. The correct option among all the options that are given in the question is the third option or the penultimate option. I hope that the answer has actually come to your help.

B) friction causes the heat, but is also the force that stops the car from crashing!
The pads, disc, drum, etc. of the brake system are designed to absorb most of the heat produced from the friction of braking.