The Laplace transform of the signal t u(t) * cos 2 t u(t) is _____________

• A. ( frac{1}{s(s^2+4 ^2)} )
• B. ( frac{2 }{s^2 (s^2+4 ^2)} )
• C. ( frac{1}{s^2 (s^2+4 ^2)} )
• D. ( frac{s^3}{(s^2+4 ^2)} )