When one arm of a U-tube manometer is connected to a gas supply, the levels of mercury in the two arms of the U-tube is shown in the figure above, if the atmospheric pressure is 76.0cm hg, the gas pressure is
-
A.
62.6cm hg -
B.
72.5cm hg -
C.
79.5cm hg -
D.
85.9cm hg