The narrow band FM signal is 10 cos (2π1000t + 0.2 sin (2π100t)) what is the instantaneous frequency:

• A. 1000 + 20 cos (2π100t)
• B. 2000 + 10 cos (2π100t)
• C. 1000 + 10 sin (2π100t)
• D. 2 cos (2π100t)