Final answer:
To keep your POS Passcode secure, you should change it regularly, avoid sharing it or writing it down, and use non-guessable codes.
Step-by-step explanation:
The best practice to keep your POS Passcode secure is C. Change it regularly. To ensure the safety of your financial information including protecting your credit and debit cards, it is important that you do not share passcodes with even trusted colleagues, avoid using easily guessable codes, and never write down your passcodes in plain sight where others can see them. Additionally, taking steps such as using anti-virus software on your computer, securing your mailbox from theft, and notifying your bank of any personal information changes can help enhance the overall security of your personal and financial data.