You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

Sandy and Keith plan to move a 6-kilogram block. If they wanted to calculate the mechanical energy required to move the block, what units would they use to report their answer?
(A) joules (B) kilowatts (C) kilometers (D) volts
A