Which of the following is true about elements? a. atoms of all elements contain the same number of protons, but the number of neutrons is different for every element. b. atoms of all elements contain neutrons, but they do not all contain protons. c. atoms of all elements contain electrons, but they do not all contain protons. d. atoms of all elements contain protons, but the number of protons is different for every element.

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.