In compressed air tunnelling, the volume of free air provided is
A
6 m<sup>3</sup> per second per m<sup>2</sup> of face area
B
6 m<sup>3</sup> per minute per m<sup>2</sup> of face area
C
20 m<sup>3</sup> per minute per m<sup>2</sup> of face area
D
6 m<sup>3</sup> per hour per m<sup>2</sup> of face area
Correct Answer: 6 m<sup>3</sup> per minute per m<sup>2</sup> of face area