A) all mechanical waves need a medium to travel through.
This is true because mechanical waves move in a wave like manner at the atomic level. This is why an table vibrates when you put a speaker on top of it .
Answer: Atom/element
Explanation: Since matter cannot be created or destroyed, the number of atoms has to be equal on both sides of the equation.
The best steps that should always be used for effective problem solving would be C. Developing a plan and then implementing the plan.
