If the rate constant for a first order reaction is k,the time (t) required for the completion of 90% of the reaction is given by :-

Question

( A ) $t =\frac{ 2.303}{k}$
( B ) $t = \frac{4.606}{k}$
( C ) $t = \frac{0.693}{k}$
( D ) $t =\frac{ 6.909}{k}$