Final answer:
A professional approach avoids directly mentioning Martina's lunch break and instead offers assistance or to take a message, maintaining a positive customer interaction.
Step-by-step explanation:
A more professional way to inform a customer that Martina is not available because she is still at lunch would be:
"Thank you for calling. Martina is currently away from her desk, but I can assist you or take a message. May I ask who's calling and whether there's something specific you need help with?"
This response is professional as it acknowledges the customer's call, provides immediate assistance, offers an alternative action (taking a message), and maintains a positive interaction without directly stating Martina's absence due to lunch.