I'm not certain if I'm right but I think it's C.
Equilibrium is a chemistry term that means "at the same rate" so I assume it's the word that's out of place here.
service contract is a business agreement between a contractor and customer covering the maintenance and servicing of equipment over a specified period.warranty is a written guarantee, issued to the purchaser of an article by its manufacturer, promising to repair or replace it if necessary within a specified period of time.
Answer:
Thanks have a lovely day <3