Greta describes herself as someone who gets things “stuck in my head,” especially if it worries her. Based on this text, Greta shows this in her activism by being

The correct answer is C) relentless.

Greta’s description of getting things “stuck in my head,” especially if it worries her, suggests that she is persistent and determined in her activism. This relentless mindset drives her to advocate for causes she cares about, rather than giving up or being compliant.