Final answer:
The polite way to inform a guest at the speaker that you need a moment while entering their order is to say "Bear with me just a moment, please" with a respectful tone.
Step-by-step explanation:
When keying in an order at the speaker, it's crucial to communicate effectively with the guest. The most professional approach among the options given is: "Bear with me just a moment, please". This polite phrase acknowledges the guest's time while also indicating that you need a brief moment to complete the task at hand. It's important to maintain a cordial and respectful tone, as the way you interact with the guest can impact their overall experience.