What is an appropriate response to someone saying "merci" in French?

Read also:

• What do you think is the #1 cause of why relationships nowadays don't seem to last long?
• How would you respond to Rep. Nancy Mace's claim that the GOP platform is more in line with what the American people want compared to the left?
• Which branch of engineering is better: ECE or Civil?
• What are your darkest taboo confessions?
• Have you ever been forced to undress for money just once?
• Why is the word "democracy" not in the preamble of the US Constitution?
• How do people who are deaf learn sign language? Is it typically taught by parents at a young age or are there programs available for learning it later in life?
• Unvaccinated cat in St. Johns County prompts 60-day rabies alert - News4JAX
• How do I write a character’s physical description without it feeling unnatural and clunky? I’m able to describe their hair and body relatively easily because my writing puts emphasis on small movements and fidgeting, but I can’t describe faces.
• Why does my vagina smell sort of fishy/musty days after sex when my boyfriend ejaculates in me? There isn’t any itching or burning when urinating, so I don't think I have BV. It just doesn't smell like me.