Find the Laplace transform of e-at u(t) and its ROC.

• A. \(\frac{1}{s-a}\), Re{s}>-a
• B. \(\frac{1}{s}\), Re{s}>a
• C. \(\frac{1}{s×a}\), Re{s}>a
• D. \(\frac{1}{s+a}\), Re{s}>-a