A copper rod with initial length l0 is pulled by a force. The instantaneous length of the rod is given by \(l = {l_0}\left( {1 + 2{e^{4t}}} \right)\) where t represents time. True strain rate at t = 0 is:

• A. \(\frac{1}{3}\)
• B. \(\frac{8}{3}\)
• C. \(\frac{4}{3}\)
• D. \(\frac{2}{3}\)