Select the correct active form of the given sentence.
A close watch was kept by the police on the bus driver due to his suspicious activities.
1
The police are keeping a close watch on the bus driver due to his suspicious activities.
2
A close watch on the bus driver due to his suspicious activities was being kept by police.
3
The police, due to his suspicious activities, have been keeping a close watch on the bus driver.
4
The police kept a close watch on the bus driver due to his suspicious activities.