A customer reports high data usage on a smartphone that reaches its monthly data limit...

Since both developer mode and the ability to install apps from unknown sources are enabled, the technician should check for Malicious applications (Option B). Unknown sources can allow unverified apps that may include malware or apps that use excessive background data without the user's knowledge. Checking for malicious apps is essential in this scenario.

Storage cache (Option A) would not typically cause high data usage.

Privacy settings (Option C) control data sharing and permissions but don't directly impact data usage.

Permissions (Option D) might help identify apps using data, but the focus should be on apps that could be malicious.

CompTIA A+ Core 2 References:

2.7 - Explain common methods for securing mobile devices, including detecting and preventing malware​.