A vector \[\overrightarrow{a}\] is turned without a change in its length through a small angle \[d\theta .\]The value of \[|\Delta \overrightarrow{a}|\] and \[\Delta a\] are respectively

• A.             \[0,\,a\,d\theta \]
• B.                                         \[a\,d\theta ,\,0\,\]
• C.             0, 0
• D.             None of these