The concentration of the dust particles of the size 0.5 to 5 microns adjacent to the working face should not be more than

Which of the following are percussion drills?
(i) Shot drill
(ii) Diamond drill
(iii) Wagon drill
(iv) Churn drill

A. (i) and (ii) are correct

B. (iii) and (iv) are correct

C. (i) and (iv) are correct

D. (ii) and (iii) are correct

Which of the following lining material is useful for shield driven tunnels in sub aqueous regions?

A. Stone masonry

B. Timber

C. Cast iron

D. Cement concrete

Which of the following methods of tunneling is used for long tunnels at great depths?

A. Army method

B. Needle beam method

C. Austrian method

D. English method

Drifters can be used to drill

A. Only up holes

B. Only down holes

C. Horizontal or up holes

D. Horizontal down or up holes