Cho vectơ \(\overrightarrow {\,a\,}  = \left( {1;2;3} \right),{\rm{ }}\overrightarrow {\,b\,}  = \left( {2;5;6} \right)\).

A. \(\cos \left( {\overrightarrow {\,b\,} ,\overrightarrow {\,c\,} } \right) = \frac{{\sqrt 6 }}{3}\)

B. \(\overrightarrow {\,a\,} .\overrightarrow {\,b\,}  = 30\)

C. \(\overrightarrow {\,a\,}  - \overrightarrow {\,b\,}  = \left( { - 1; - 3; - 3} \right)\)

D. \(\overrightarrow {\,a\,}  + \overrightarrow {\,b\,}  = \left( {3;7;9} \right)\)