The difference of heights of the tunnels above rail tops of BG and MG tracks is kept

A. (i) and (ii) are correct B. (iii) and (iv) are correct C. (i) and (iv) are correct D. (ii) and (iii) are correct

A. Stone masonry B. Timber C. Cast iron D. Cement concrete

A. Army method B. Needle beam method C. Austrian method D. English method

A. Only up holes B. Only down holes C. Horizontal or up holes D. Horizontal down or up holes