Rút gọn: \(P = \frac{{\sqrt {10}  + \sqrt {19} }}{{2\sqrt 5  + \sqrt {38} }}\)

A. \(\sqrt 2 \)

B. \(\frac{1}{{\sqrt 2 }}\)

C. \(2\sqrt 3 \)

D. \(\frac{1}{{2\sqrt 3 }}\)