Final answer:
A generator converts mechanical energy into electrical energy by electromagnetic induction, thus the answer is a) Generator.
Step-by-step explanation:
A generator changes mechanical energy into electrical energy through a process known as electromagnetic induction. An electric generator works by converting mechanical work into electric energy; it induces an electromotive force (emf) by rotating a coil within a magnetic field. Essentially, the mechanical motion of the coil through the magnetic field generates an electric current due to the principles of electromagnetic induction. Therefore, the correct answer to the question is:a) Generator