The most likely cause for a lady with a history of Rheumatoid Arthritis (RA) presenting with a one-day history of pain in the right hand, fever (100.8°F), and physical examination findings of swelling at the right 2nd metacarpophalangeal joint (MCP) with guarding and significant tenderness to palpation is:
a) Septic arthritis
b) Osteoarthritis flare
c) Gouty arthritis
d) Rheumatoid arthritis exacerbation