A computer is slow, unknown messages appear, and unknown applications open. What is the most responsible step?

Correct answer: Run a security scan and avoid suspicious applications

Slowness, unexpected messages, and unknown applications can indicate malware or another security problem, although they do not prove one by themselves. A security scan is a suitable first response, and avoiding suspicious links or programs prevents further harm. Clicking everything, sharing passwords, or deleting all files blindly can worsen the situation and destroy useful evidence.