The correct answer is D. Restart the device.

According to CompTIA A+ Core 1 220-1201 objectives under Mobile Devices and Security:

Warning messages like this can be caused by malicious pop-ups or temporary software glitches. Restarting the device is the safest and quickest first step to clear temporary processes, refresh the system, and remove transient malware or pop-up overlays.

This approach addresses the issue without risking data loss or unnecessary downtime.

Why the other options are incorrect:

A. Force close all running applications: May help if a specific app is causing the pop-up, but restarting achieves this more reliably and fully resets background processes.

B. Replace the tablet with a newer device: Unnecessary and costly for a potentially temporary software issue.

C. Reset the device to default settings: This is a last-resort action, as it erases personal data and settings; it is not the first step.