The phrase that best describe the word "energy" is letter "C. the ability to do work". The unit most commonly used to express energy is Joules (J) which is also derived from the equation of work which is the product of force and the distance that a body moves parallel to the force applied.
The difference between plant cells and animal cells is that most animal cells are round whereas most plant cells are rectangular. Plant cells have a rigid cell wall that surrounds the cell membrane. Animal cells do not have a cell wall.
