There are many sayings and metaphors about flirting, which one could be found in a machine shop?\nOptions:\n- feelings\n- sexual excitement\n- sparks fly\n- problems\n- unwanted pregnancy
Stream of thoughts:
sparks fly
Sparks fly in flirting means having a spark between two people.

A machine shop has various machines that can have spark fly.

.

So, the final answer is sparks fly