Select the correct active voice of the given sentence.
The states of Maharashtra and Gujarat have been alerted about the impending cyclone by NDRF.

A

NDRF has alerted the states of Maharashtra and Gujarat about the impending cyclone.

B

NDRF alerted the states of Maharashtra and Gujarat about the impending cyclone.

C

NDRF was alerting the states of Maharashtra and Gujarat about the impending cyclone.

D

NDRF has been alerting the states of Maharashtra and Gujarat about the impending cyclone.