Final answer:
Ren agrees to have a drink (option C), as indicated by their statement that they'll have a beer after Harry's invitation to dinner.
Step-by-step explanation:
Ren agrees to C) Having a drink. The dialogue indicates that Harry suggests it's time for a meal, subtly implying that they could accompany it with drinks. When Ren responds with 'Sounds good, then I'll have a beer,' it shows that Ren is agreeing to the idea of consuming a beverage, specifically a beer, which aligns with the context set by Harry's invitation to come down for some dinner and implicitly also the accompanying drinks.