Which process can transfer energy to a solid metal block

Eneregy is the ability to to do work it takes work to heat someone heat is energy put the solid metal block in a campfire and heat it up tada wait, we need the options, nevermind

-- Heat conduction can, like when you put a hot iron down
on the metal block.

-- Radiation can, like when you put the block outside
in the sun.

-- Electric current can, like when you connect wires from
the block to both terminals of a battery.

-- Doing mechanical work on it can, like when you carry the block
upstairs to your bedroom, giving it gravitational potential energy.

-- Motion can, like when you drop the block out of your bedroom
window, and the force of gravity gives it kinetic energy.

The anwser is: wave a has a greater pitch and frequency.