Choose the best meaning for the underlined simile. " Her body was like a machine." Mia was training for the Olympics. She did a hundred push-ups and a thousand sit-ups everyday. Every other day, she ran for five miles. Her body was like a machine.

a) Mia uses electronic gym equipment.
b) Part of Mia's body was robotic.
c) Mia often gets bored, so she exercises.
d) Mia consistently completes her exercises.
Note: b or d??? what is the best answer??? please help.