The depths from the soil surface to subsurface tile drains, impermeable soil layer and the highest water table are measured as $2.8 \mathrm{~m}, 5.0 \mathrm{~m}$ and $0.8 \mathrm{~m}$, respectively. The effective hydraulic head for drainage in meter is
(A) 0.8
(B) 2.0
(C) 2.2
(D) 4.2
The depths from the soil surface to subsurface tile drains, impermeable soil layer and the highest water table are measured as $2.8 \mathrm{~m}, 5.0 \mathrm{~m}$ and $0.8 \mathrm{~m}$, respectively. The effective hydraulic head for drainage in meter is
(A) 0.8
(B) 2.0
(C) 2.2
(D) 4.2