A: Not secure at all.
It is privy to the front desk staff, management, leadership – almost all in unencrypted format.
Unless you are staying at some shady facility, the law requires a drivers license or other ID in order to reserve a room. With your state-issued ID in hand, your information is monetized when sent to the hotel ownership (some other multinational Corp) for sales and marketing.
It is likely sold to other advertisers.
Not to mention that local, state, and federal law enforcement have free access to this information.
All. That. Said…
If one thinks they have to concern themself with security and privacy at the level of hotels, it’s time to wake up! They are several blocks back in the line of people and organizations sniffing through your data.