Which sentence gives an example of an analogy?

a. The scent is like a time machine, returning me to the café near where I waited for the bus every morning.
b. To Webster, the sound of Sarah’s violin playing was like a gentle mountain stream.
c. The new engineer in the fossil fuels division is definitely a diamond in the rough.
d. The grass in the front yard made walking to the mailbox like trudging through the Amazon rain forest.

a. The scent is like a time machine, returning me to the café near where I waited for the bus every morning.